Image encoding/decoding method and device, and recording medium in which bitstream is stored

ABSTRACT

Disclosed herein is a method of decoding an image. The method includes generating an inter prediction block by performing inter prediction with respect to a current block, generating an intra prediction block by performing intra prediction with respect to the current block, determining a first weight and a second weight, and generating a final prediction block by respectively applying the first weight and the second weight to the inter prediction block and the intra prediction block. The generating of the intra prediction block includes generating the intra prediction block using a predefined intra prediction mode.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S.application Ser. No. 17/890,972, filed on Aug. 18, 2022, which is acontinuation application of U.S. application Ser. No. 17/420,106, filedon Jun. 30, 2021, which was the National Stage of InternationalApplication No. PCT/KR2019/018630 filed on Dec. 27, 2019, which claimspriority under 35 U.S.C. § 119(a) to Korean Patent Applications:KR10-2018-00174189, filed on Dec. 31, 2018, KR10-2019-0053588, filed onMay 8, 2019, KR10-2019-0074413, filed on Jun. 21, 2019, andKR10-2019-0094181, filed on Aug. 2, 2019, with the Korean IntellectualProperty Office, which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to an image encoding/decoding method andapparatus, and a recording medium for storing a bitstream. Moreparticularly, the present invention relates to an imageencoding/decoding method and apparatus using combined inter intraprediction.

BACKGROUND ART

Recently, the demand for high resolution and quality images such as highdefinition (HD) or ultra-high definition (UHD) images has increased invarious applications. As the resolution and quality of images areimproved, the amount of data correspondingly increases. This is one ofthe causes of increase in transmission cost and storage cost whentransmitting image data through existing transmission media such aswired or wireless broadband channels or when storing image data. Inorder to solve such problems with high resolution and quality imagedata, a high efficiency image encoding/decoding technique is required.

There are various video compression techniques such as an interprediction technique of predicting the values of pixels within a currentpicture from the values of pixels within a preceding picture or asubsequent picture, an intra prediction technique of predicting thevalues of pixels within a region of a current picture from the values ofpixels within another region of the current picture, a transform andquantization technique of compressing the energy of a residual signal,and an entropy coding technique of allocating frequently occurring pixelvalues with shorter codes and less occurring pixel values with longercodes.

A conventional image encoding/decoding method and apparatus is anencoding/decoding method and apparatus based on intra prediction or anencoding/decoding method and apparatus based on inter prediction andthus has a lower compression ratio.

DISCLOSURE Technical Problem

An object of the present invention is to provide an imageencoding/decoding method and apparatus for performing combined interintra prediction in consideration of the structure and characteristicsof a block, in order to improve encoding efficiency.

Another object of the present invention is to provide an imageencoding/decoding method and apparatus for constructing an intraprediction candidate mode in consideration of the structure andcharacteristics of a block, in order to improve encoding efficiency.

Another object of the present invention is to provide an imageencoding/decoding method and apparatus for generating a final predictionblock by giving weights to a prediction block generated through intraprediction and a prediction block generated through inter prediction andcombining the prediction blocks in consideration of the structure andcharacteristics of a block, in order to improve encoding efficiency.

Technical Solution

A method of decoding an image according to an embodiment of the presentinvention includes generating an inter prediction block by performinginter prediction with respect to a current block, generating an intraprediction block by performing intra prediction with respect to thecurrent block, determining a first weight and a second weight, andgenerating a final prediction block by respectively applying the firstweight and the second weight to the inter prediction block and the intraprediction block. The generating of the intra prediction block includesgenerating the intra prediction block using a predefined intraprediction mode.

In the method of decoding the image of the present invention, thepredefined intra prediction mode may be a non-directional intraprediction mode.

In the method of decoding the image of the present invention, thepredefined intra prediction mode may be a PLANAR intra prediction mode.

In the method of decoding the image of the present invention, thedetermining of the first weight and the second weight may includedetermining the first weight and the second weight based on a predictionmode of at least one neighbor block adjacent to the current block.

In the method of decoding the image of the present invention, thedetermining of the first weight and the second weight may includedetermining the first weight and the second weight based on the numberof neighbor blocks decoded in an intra prediction mode among a pluralityof neighbor blocks adjacent to the current block.

In the method of decoding the image of the present invention, theplurality of neighbor blocks may include a left neighbor block adjacentto a left of the current block and a top neighbor block adjacent to atop of the current block.

In the method of decoding the image of the present invention, the methodmay further include determining whether a prediction mode of the currentblock is a combined inter intra mode, and, when the prediction mode ofthe current block is the combined inter intra mode, at least one of DMVR(Decoder-side Motion Vector Refinement), BDOF (Bi-Directional OpticalFlow) or BCW (Bi-prediction with CU-level weight) may not be performed.

A method of encoding an image according to an embodiment of the presentinvention includes generating an inter prediction block by performinginter prediction with respect to a current block, generating an intraprediction block by performing intra prediction with respect to thecurrent block, determining a first weight and a second weight, andgenerating a final prediction block by respectively applying the firstweight and the second weight to the inter prediction block and the intraprediction block. The generating of the intra prediction block includesgenerating the intra prediction block using a predefined intraprediction mode.

In the method of encoding the image of the present invention, thepredefined intra prediction mode may be a non-directional intraprediction mode.

In the method of encoding the image of the present invention, thepredefined intra prediction mode may be a PLANAR intra prediction mode.

In the method of encoding the image of the present invention, thedetermining of the first weight and the second weight may includedetermining the first weight and the second weight based on a predictionmode of at least one neighbor block adjacent to the current block.

In the method of encoding the image of the present invention, thedetermining of the first weight and the second weight may includedetermining the first weight and the second weight based on the numberof neighbor blocks decoded in an intra prediction mode among a pluralityof neighbor blocks adjacent to the current block.

In the method of encoding the image of the present invention, theplurality of neighbor blocks may include a left neighbor block adjacentto a left of the current block and a top neighbor block adjacent to atop of the current block.

In the method of encoding the image of the present invention, the methodmay further include determining whether a prediction mode of the currentblock is a combined inter intra mode, and, when the prediction mode ofthe current block is the combined inter intra mode, at least one of DMVR(Decoder-side Motion Vector Refinement), BDOF (Bi-Directional OpticalFlow) or BCW (Bi-prediction with CU-level weight) may not be performed.

In a non-transitory computer-readable recording medium for storing abitstream generated by an image encoding method according to anotherembodiment of the present invention, the image encoding method includesgenerating an inter prediction block by performing inter prediction withrespect to a current block, generating an intra prediction block byperforming intra prediction with respect to the current block,determining a first weight and a second weight, and generating a finalprediction block by respectively applying the first weight and thesecond weight to the inter prediction block and the intra predictionblock. The generating of the intra prediction block includes generatingthe intra prediction block using a predefined intra prediction mode.

Advantageous Effects

According to the present invention, it is possible to provide an imageencoding/decoding method and apparatus with improved compressionefficiency.

According to the present invention, it is possible to provide an imageencoding/decoding method and apparatus for performing combined interintra prediction in consideration of the structure and characteristicsof a block, in order to improve encoding efficiency.

According to the present invention, it is possible to provide a combinedinter intra prediction method of using a weight determined inconsideration of the structure and characteristics of a block, in orderto improve encoding efficiency.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a configuration of an encodingapparatus according to an embodiment to which the present invention isapplied.

FIG. 2 is a block diagram showing a configuration of a decodingapparatus according to an embodiment and to which the present inventionis applied.

FIG. 3 is a view schematically showing a partition structure of an imagewhen encoding and decoding the image.

FIG. 4 is a view showing an intra-prediction process.

FIG. 5 is a diagram illustrating an embodiment of an inter-pictureprediction process.

FIG. 6 is a diagram illustrating a transform and quantization process.

FIG. 7 is a diagram illustrating reference samples capable of being usedfor intra prediction.

FIG. 8 is a flowchart illustrating an encoding/decoding method usingcombined inter intra prediction.

FIG. 9 is a flowchart illustrating a method of assigning a predictionmode to an MPM candidate mode list.

FIG. 10 is a flowchart illustrating a method of assigning a predictionmode to an MPM candidate mode list.

FIG. 11 is a view showing the location of a neighbor block.

FIGS. 12 and 13 are views showing a plurality of zones, to which weightsof combined inter intra prediction are applied, in a current block.

FIG. 14 is a view showing a single zone, to which a weight of combinedinter intra prediction is applied, in a current block.

FIGS. 15 to 17 are views illustrating the combining order of an intraprediction block and an inter prediction block in inter-intracombination.

FIG. 18 is a view illustrating an image decoding method according to anembodiment of the present invention.

MODE FOR INVENTION

A variety of modifications may be made to the present invention andthere are various embodiments of the present invention, examples ofwhich will now be provided with reference to drawings and described indetail. However, the present invention is not limited thereto, althoughthe exemplary embodiments can be construed as including allmodifications, equivalents, or substitutes in a technical concept and atechnical scope of the present invention. The similar reference numeralsrefer to the same or similar functions in various aspects. In thedrawings, the shapes and dimensions of elements may be exaggerated forclarity. In the following detailed description of the present invention,references are made to the accompanying drawings that show, by way ofillustration, specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to implement the present disclosure. Itshould be understood that various embodiments of the present disclosure,although different, are not necessarily mutually exclusive. For example,specific features, structures, and characteristics described herein, inconnection with one embodiment, may be implemented within otherembodiments without departing from the spirit and scope of the presentdisclosure. In addition, it should be understood that the location orarrangement of individual elements within each disclosed embodiment maybe modified without departing from the spirit and scope of the presentdisclosure. The following detailed description is, therefore, not to betaken in a limiting sense, and the scope of the present disclosure isdefined only by the appended claims, appropriately interpreted, alongwith the full range of equivalents to what the claims claim.

Terms used in the specification, ‘first’, ‘second’, etc. can be used todescribe various components, but the components are not to be construedas being limited to the terms. The terms are only used to differentiateone component from other components. For example, the ‘first’ componentmay be named the ‘second’ component without departing from the scope ofthe present invention, and the ‘second’ component may also be similarlynamed the ‘first’ component. The term ‘and/or’ includes a combination ofa plurality of items or any one of a plurality of terms.

It will be understood that when an element is simply referred to asbeing ‘connected to’ or ‘coupled to’ another element without being‘directly connected to’ or ‘directly coupled to’ another element in thepresent description, it may be ‘directly connected to’ or ‘directlycoupled to’ another element or be connected to or coupled to anotherelement, having the other element intervening therebetween. In contrast,it should be understood that when an element is referred to as being“directly coupled” or “directly connected” to another element, there areno intervening elements present.

Furthermore, constitutional parts shown in the embodiments of thepresent invention are independently shown so as to representcharacteristic functions different from each other. Thus, it does notmean that each constitutional part is constituted in a constitutionalunit of separated hardware or software. In other words, eachconstitutional part includes each of enumerated constitutional parts forconvenience. Thus, at least two constitutional parts of eachconstitutional part may be combined to form one constitutional part orone constitutional part may be divided into a plurality ofconstitutional parts to perform each function. The embodiment where eachconstitutional part is combined and the embodiment where oneconstitutional part is divided are also included in the scope of thepresent invention, if not departing from the essence of the presentinvention.

The terms used in the present specification are merely used to describeparticular embodiments, and are not intended to limit the presentinvention. An expression used in the singular encompasses the expressionof the plural, unless it has a clearly different meaning in the context.In the present specification, it is to be understood that terms such as“including”, “having”, etc. are intended to indicate the existence ofthe features, numbers, steps, actions, elements, parts, or combinationsthereof disclosed in the specification, and are not intended to precludethe possibility that one or more other features, numbers, steps,actions, elements, parts, or combinations thereof may exist or may beadded. In other words, when a specific element is referred to as being“included”, elements other than the corresponding element are notexcluded, but additional elements may be included in embodiments of thepresent invention or the scope of the present invention.

In addition, some of constituents may not be indispensable constituentsperforming essential functions of the present invention but be selectiveconstituents improving only performance thereof. The present inventionmay be implemented by including only the indispensable constitutionalparts for implementing the essence of the present invention except theconstituents used in improving performance. The structure including onlythe indispensable constituents except the selective constituents used inimproving only performance is also included in the scope of the presentinvention.

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. In describingexemplary embodiments of the present invention, well-known functions orconstructions will not be described in detail since they mayunnecessarily obscure the understanding of the present invention. Thesame constituent elements in the drawings are denoted by the samereference numerals, and a repeated description of the same elements willbe omitted.

Hereinafter, an image may mean a picture configuring a video, or maymean the video itself. For example, “encoding or decoding or both of animage” may mean “encoding or decoding or both of a moving picture”, andmay mean “encoding or decoding or both of one image among images of amoving picture.”

Hereinafter, terms “moving picture” and “video” may be used as the samemeaning and be replaced with each other.

Hereinafter, a target image may be an encoding target image which is atarget of encoding and/or a decoding target image which is a target ofdecoding. Also, a target image may be an input image inputted to anencoding apparatus, and an input image inputted to a decoding apparatus.Here, a target image may have the same meaning with the current image.

Hereinafter, terms “image”, “picture, “frame” and “screen” may be usedas the same meaning and be replaced with each other.

Hereinafter, a target block may be an encoding target block which is atarget of encoding and/or a decoding target block which is a target ofdecoding. Also, a target block may be the current block which is atarget of current encoding and/or decoding. For example, terms “targetblock” and “current block” may be used as the same meaning and bereplaced with each other.

Hereinafter, terms “block” and “unit” may be used as the same meaningand be replaced with each other. Or a “block” may represent a specificunit.

Hereinafter, terms “region” and “segment” may be replaced with eachother.

Hereinafter, a specific signal may be a signal representing a specificblock. For example, an original signal may be a signal representing atarget block. A prediction signal may be a signal representing aprediction block. A residual signal may be a signal representing aresidual block.

In embodiments, each of specific information, data, flag, index, elementand attribute, etc. may have a value. A value of information, data,flag, index, element and attribute equal to “0” may represent a logicalfalse or the first predefined value. In other words, a value “0”, afalse, a logical false and the first predefined value may be replacedwith each other. A value of information, data, flag, index, element andattribute equal to “1” may represent a logical true or the secondpredefined value. In other words, a value “1”, a true, a logical trueand the second predefined value may be replaced with each other.

When a variable i or j is used for representing a column, a row or anindex, a value of i may be an integer equal to or greater than 0, orequal to or greater than 1. That is, the column, the row, the index,etc. may be counted from 0 or may be counted from 1.

Description of Terms

Encoder: means an apparatus performing encoding. That is, means anencoding apparatus.

Decoder: means an apparatus performing decoding. That is, means adecoding apparatus.

Block: is an M×N array of a sample. Herein, M and N may mean positiveintegers, and the block may mean a sample array of a two-dimensionalform. The block may refer to a unit. A current block my mean an encodingtarget block that becomes a target when encoding, or a decoding targetblock that becomes a target when decoding. In addition, the currentblock may be at least one of an encode block, a prediction block, aresidual block, and a transform block.

Sample: is a basic unit constituting a block. It may be expressed as avalue from 0 to 2^(Bd)−1 according to a bit depth (B_(d)). In thepresent invention, the sample may be used as a meaning of a pixel. Thatis, a sample, a pel, a pixel may have the same meaning with each other.

Unit: may refer to an encoding and decoding unit. When encoding anddecoding an image, the unit may be a region generated by partitioning asingle image. In addition, the unit may mean a subdivided unit when asingle image is partitioned into subdivided units during encoding ordecoding. That is, an image may be partitioned into a plurality ofunits. When encoding and decoding an image, a predetermined process foreach unit may be performed. A single unit may be partitioned intosub-units that have sizes smaller than the size of the unit. Dependingon functions, the unit may mean a block, a macroblock, a coding treeunit, a code tree block, a coding unit, a coding block), a predictionunit, a prediction block, a residual unit), a residual block, atransform unit, a transform block, etc. In addition, in order todistinguish a unit from a block, the unit may include a luma componentblock, a chroma component block associated with the luma componentblock, and a syntax element of each color component block. The unit mayhave various sizes and forms, and particularly, the form of the unit maybe a two-dimensional geometrical figure such as a square shape, arectangular shape, a trapezoid shape, a triangular shape, a pentagonalshape, etc. In addition, unit information may include at least one of aunit type indicating the coding unit, the prediction unit, the transformunit, etc., and a unit size, a unit depth, a sequence of encoding anddecoding of a unit, etc.

Coding Tree Unit: is configured with a single coding tree block of aluma component Y, and two coding tree blocks related to chromacomponents Cb and Cr. In addition, it may mean that including the blocksand a syntax element of each block. Each coding tree unit may bepartitioned by using at least one of a quad-tree partitioning method, abinary-tree partitioning method and ternary-tree partitioning method toconfigure a lower unit such as coding unit, prediction unit, transformunit, etc. It may be used as a term for designating a sample block thatbecomes a process unit when encoding/decoding an image as an inputimage. Here, the quad-tree may mean a quarternary-tree.

When the size of the coding block is within a predetermined range, thedivision is possible using only quad-tree partitioning. Here, thepredetermined range may be defined as at least one of a maximum size anda minimum size of a coding block in which the division is possible usingonly quad-tree partitioning. Information indicating a maximum/minimumsize of a coding block in which quad-tree partitioning is allowed may besignaled through a bitstream, and the information may be signaled in atleast one unit of a sequence, a picture parameter, a tile group, or aslice (segment). Alternatively, the maximum/minimum size of the codingblock may be a fixed size predetermined in the coder/decoder. Forexample, when the size of the coding block corresponds to 256×256 to64×64, the division is possible only using quad-tree partitioning.Alternatively, when the size of the coding block is larger than the sizeof the maximum conversion block, the division is possible only usingquad-tree partitioning. Herein, the block to be divided may be at leastone of a coding block and a transform block. In this case, informationindicating the division of the coded block (for example, split flag) maybe a flag indicating whether or not to perform the quad-treepartitioning. When the size of the coding block falls within apredetermined range, the division is possible only using binary tree orternary tree partitioning. In this case, the above description of thequad-tree partitioning may be applied to binary tree partitioning orternary tree partitioning in the same manner.

Coding Tree Block: may be used as a term for designating any one of a Ycoding tree block, Cb coding tree block, and Cr coding tree block.

Neighbor Block: may mean a block adjacent to a current block. The blockadjacent to the current block may mean a block that comes into contactwith a boundary of the current block, or a block positioned within apredetermined distance from the current block. The neighbor block maymean a block adjacent to a vertex of the current block. Herein, theblock adjacent to the vertex of the current block may mean a blockvertically adjacent to a neighbor block that is horizontally adjacent tothe current block, or a block horizontally adjacent to a neighbor blockthat is vertically adjacent to the current block.

Reconstructed Neighbor block: may mean a neighbor block adjacent to acurrent block and which has been already spatially/temporally encoded ordecoded. Herein, the reconstructed neighbor block may mean areconstructed neighbor unit. A reconstructed spatial neighbor block maybe a block within a current picture and which has been alreadyreconstructed through encoding or decoding or both. A reconstructedtemporal neighbor block is a block at a corresponding position as thecurrent block of the current picture within a reference image, or aneighbor block thereof.

Unit Depth: may mean a partitioned degree of a unit. In a treestructure, the highest node (Root Node) may correspond to the first unitwhich is not partitioned. Also, the highest node may have the leastdepth value. In this case, the highest node may have a depth of level 0.A node having a depth of level 1 may represent a unit generated bypartitioning once the first unit. A node having a depth of level 2 mayrepresent a unit generated by partitioning twice the first unit. A nodehaving a depth of level n may represent a unit generated by partitioningn-times the first unit. A Leaf Node may be the lowest node and a nodewhich cannot be partitioned further. A depth of a Leaf Node may be themaximum level. For example, a predefined value of the maximum level maybe 3. A depth of a root node may be the lowest and a depth of a leafnode may be the deepest. In addition, when a unit is expressed as a treestructure, a level in which a unit is present may mean a unit depth.

Bitstream: may mean a bitstream including encoding image information.

Parameter Set: corresponds to header information among a configurationwithin a bitstream. At least one of a video parameter set, a sequenceparameter set, a picture parameter set, and an adaptation parameter setmay be included in a parameter set. In addition, a parameter set mayinclude a slice header, a tile group header, and tile headerinformation. The term “tile group” means a group of tiles and has thesame meaning as a slice.

An adaptation parameter set may mean a parameter set that can be sharedby being referred to in different pictures, subpictures, slices, tilegroups, tiles, or bricks. In addition, information in an adaptationparameter set may be used by referring to different adaptation parametersets for a subpicture, a slice, a tile group, a tile, or a brick insidea picture.

In addition, regarding the adaptation parameter set, differentadaptation parameter sets may be referred to by using identifiers ofdifferent adaptation parameter sets for a subpicture, a slice, a tilegroup, a tile, or a brick inside a picture.

In addition, regarding the adaptation parameter set, differentadaptation parameter sets may be referred to by using identifiers ofdifferent adaptation parameter sets for a slice, a tile group, a tile,or a brick inside a subpicture.

In addition, regarding the adaptation parameter set, differentadaptation parameter sets may be referred to by using identifiers ofdifferent adaptation parameter sets for a tile or a brick inside aslice.

In addition, regarding the adaptation parameter set, differentadaptation parameter sets may be referred to by using identifiers ofdifferent adaptation parameter sets for a brick inside a tile.

Information on an adaptation parameter set identifier may be included ina parameter set or a header of the subpicture, and an adaptationparameter set corresponding to the adaptation parameter set identifiermay be used for the subpicture.

The information on the adaptation parameter set identifier may beincluded in a parameter set or a header of the tile, and an adaptationparameter set corresponding to the adaptation parameter set identifiermay be used for the tile.

The information on the adaptation parameter set identifier may beincluded in a header of the brick, and an adaptation parameter setcorresponding to the adaptation parameter set identifier may be used forthe brick.

The picture may be partitioned into one or more tile rows and one ormore tile columns.

The subpicture may be partitioned into one or more tile rows and one ormore tile columns within a picture. The subpicture may be a regionhaving the form of a rectangle/square within a picture and may includeone or more CTUs. In addition, at least one or more tiles/bricks/slicesmay be included within one subpicture.

The tile may be a region having the form of a rectangle/square within apicture and may include one or more CTUs. In addition, the tile may bepartitioned into one or more bricks.

The brick may mean one or more CTU rows within a tile. The tile may bepartitioned into one or more bricks, and each brick may have at leastone or more CTU rows. A tile that is not partitioned into two or moremay mean a brick.

The slice may include one or more tiles within a picture and may includeone or more bricks within a tile.

Parsing: may mean determination of a value of a syntax element byperforming entropy decoding, or may mean the entropy decoding itself.

Symbol: may mean at least one of a syntax element, a coding parameter,and a transform coefficient value of an encoding/decoding target unit.In addition, the symbol may mean an entropy encoding target or anentropy decoding result.

Prediction Mode: may be information indicating a mode encoded/decodedwith intra prediction or a mode encoded/decoded with inter prediction.

Prediction Unit: may mean a basic unit when performing prediction suchas inter-prediction, intra-prediction, inter-compensation,intra-compensation, and motion compensation. A single prediction unitmay be partitioned into a plurality of partitions having a smaller size,or may be partitioned into a plurality of lower prediction units. Aplurality of partitions may be a basic unit in performing prediction orcompensation. A partition which is generated by dividing a predictionunit may also be a prediction unit.

Prediction Unit Partition: may mean a form obtained by partitioning aprediction unit.

Reference picture list may refer to a list including one or morereference pictures used for inter prediction or motion compensation.There are several types of usable reference picture lists, including LC(List combined), L0 (List 0), L1 (List 1), L2 (List 2), L3 (List 3).

Inter prediction indicator may refer to a direction of inter prediction(unidirectional prediction, bidirectional prediction, etc.) of a currentblock. Alternatively, it may refer to the number of reference picturesused to generate a prediction block of a current block. Alternatively,it may refer to the number of prediction blocks used at the time ofperforming inter prediction or motion compensation on a current block.

Prediction list utilization flag indicates whether a prediction block isgenerated using at least one reference picture in a specific referencepicture list. An inter prediction indicator can be derived using aprediction list utilization flag, and conversely, a prediction listutilization flag can be derived using an inter prediction indicator. Forexample, when the prediction list utilization flag has a first value ofzero (0), it means that a reference picture in a reference picture listis not used to generate a prediction block. On the other hand, when theprediction list utilization flag has a second value of one (1), it meansthat a reference picture list is used to generate a prediction block.

Reference picture index may refer to an index indicating a specificreference picture in a reference picture list.

Reference picture may mean a reference picture which is referred to by aspecific block for the purposes of inter prediction or motioncompensation of the specific block. Alternatively, the reference picturemay be a picture including a reference block referred to by a currentblock for inter prediction or motion compensation. Hereinafter, theterms “reference picture” and “reference image” have the same meaningand can be interchangeably.

Motion vector may be a two-dimensional vector used for inter predictionor motion compensation. The motion vector may mean an offset between anencoding/decoding target block and a reference block. For example, (mvX,mvY) may represent a motion vector. Here, mvX may represent a horizontalcomponent and mvY may represent a vertical component.

Search range may be a two-dimensional region which is searched toretrieve a motion vector during inter prediction. For example, the sizeof the search range may be M×N. Here, M and N are both integers.

Motion vector candidate may refer to a prediction candidate block or amotion vector of the prediction candidate block when predicting a motionvector. In addition, a motion vector candidate may be included in amotion vector candidate list.

Motion vector candidate list may mean a list composed of one or moremotion vector candidates.

Motion vector candidate index may mean an indicator indicating a motionvector candidate in a motion vector candidate list. Alternatively, itmay be an index of a motion vector predictor.

Motion information may mean information including at least one of theitems including a motion vector, a reference picture index, an interprediction indicator, a prediction list utilization flag, referencepicture list information, a reference picture, a motion vectorcandidate, a motion vector candidate index, a merge candidate, and amerge index.

Merge candidate list may mean a list composed of one or more mergecandidates.

Merge candidate may mean a spatial merge candidate, a temporal mergecandidate, a combined merge candidate, a combined bi-predictive mergecandidate, or a zero merge candidate. The merge candidate may includemotion information such as an inter prediction indicator, a referencepicture index for each list, a motion vector, a prediction listutilization flag, and an inter prediction indicator.

Merge index may mean an indicator indicating a merge candidate in amerge candidate list. Alternatively, the merge index may indicate ablock from which a merge candidate has been derived, among reconstructedblocks spatially/temporally adjacent to a current block. Alternatively,the merge index may indicate at least one piece of motion information ofa merge candidate.

Transform Unit: may mean a basic unit when performing encoding/decodingsuch as transform, inverse-transform, quantization, dequantization,transform coefficient encoding/decoding of a residual signal. A singletransform unit may be partitioned into a plurality of lower-leveltransform units having a smaller size. Here,transformation/inverse-transformation may comprise at least one amongthe first transformation/the first inverse-transformation and the secondtransformation/the second inverse-transformation.

Scaling: may mean a process of multiplying a quantized level by afactor. A transform coefficient may be generated by scaling a quantizedlevel. The scaling also may be referred to as dequantization.

Quantization Parameter: may mean a value used when generating aquantized level using a transform coefficient during quantization. Thequantization parameter also may mean a value used when generating atransform coefficient by scaling a quantized level duringdequantization. The quantization parameter may be a value mapped on aquantization step size.

Delta Quantization Parameter: may mean a difference value between apredicted quantization parameter and a quantization parameter of anencoding/decoding target unit.

Scan: may mean a method of sequencing coefficients within a unit, ablock or a matrix. For example, changing a two-dimensional matrix ofcoefficients into a one-dimensional matrix may be referred to asscanning, and changing a one-dimensional matrix of coefficients into atwo-dimensional matrix may be referred to as scanning or inversescanning.

Transform Coefficient: may mean a coefficient value generated aftertransform is performed in an encoder. It may mean a coefficient valuegenerated after at least one of entropy decoding and dequantization isperformed in a decoder. A quantized level obtained by quantizing atransform coefficient or a residual signal, or a quantized transformcoefficient level also may fall within the meaning of the transformcoefficient.

Quantized Level: may mean a value generated by quantizing a transformcoefficient or a residual signal in an encoder. Alternatively, thequantized level may mean a value that is a dequantization target toundergo dequantization in a decoder. Similarly, a quantized transformcoefficient level that is a result of transform and quantization alsomay fall within the meaning of the quantized level.

Non-zero Transform Coefficient: may mean a transform coefficient havinga value other than zero, or a transform coefficient level or a quantizedlevel having a value other than zero.

Quantization Matrix: may mean a matrix used in a quantization process ora dequantization process performed to improve subjective or objectiveimage quality. The quantization matrix also may be referred to as ascaling list.

Quantization Matrix Coefficient: may mean each element within aquantization matrix. The quantization matrix coefficient also may bereferred to as a matrix coefficient.

Default Matrix: may mean a predetermined quantization matrixpreliminarily defined in an encoder or a decoder.

Non-default Matrix: may mean a quantization matrix that is notpreliminarily defined in an encoder or a decoder but is signaled by auser.

Statistic Value: a statistic value for at least one among a variable, acoding parameter, a constant value, etc. which have a computablespecific value may be one or more among an average value, a sum value, aweighted average value, a weighted sum value, the minimum value, themaximum value, the most frequent value, a median value, an interpolatedvalue of the corresponding specific values.

FIG. 1 is a block diagram showing a configuration of an encodingapparatus according to an embodiment to which the present invention isapplied.

An encoding apparatus 100 may be an encoder, a video encoding apparatus,or an image encoding apparatus. A video may include at least one image.The encoding apparatus 100 may sequentially encode at least one image.

Referring to FIG. 1 , the encoding apparatus 100 may include a motionprediction unit 111, a motion compensation unit 112, an intra-predictionunit 120, a switch 115, a subtractor 125, a transform unit 130, aquantization unit 140, an entropy encoding unit 150, a dequantizationunit 160, an inverse-transform unit 170, an adder 175, a filter unit180, and a reference picture buffer 190.

The encoding apparatus 100 may perform encoding of an input image byusing an intra mode or an inter mode or both. In addition, encodingapparatus 100 may generate a bitstream including encoded informationthrough encoding the input image, and output the generated bitstream.The generated bitstream may be stored in a computer readable recordingmedium, or may be streamed through a wired/wireless transmission medium.When an intra mode is used as a prediction mode, the switch 115 may beswitched to an intra. Alternatively, when an inter mode is used as aprediction mode, the switch 115 may be switched to an inter mode.Herein, the intra mode may mean an intra-prediction mode, and the intermode may mean an inter-prediction mode. The encoding apparatus 100 maygenerate a prediction block for an input block of the input image. Inaddition, the encoding apparatus 100 may encode a residual block using aresidual of the input block and the prediction block after theprediction block being generated. The input image may be called as acurrent image that is a current encoding target. The input block may becalled as a current block that is current encoding target, or as anencoding target block.

When a prediction mode is an intra mode, the intra-prediction unit 120may use a sample of a block that has been already encoded/decoded and isadjacent to a current block as a reference sample. The intra-predictionunit 120 may perform spatial prediction for the current block by using areference sample, or generate prediction samples of an input block byperforming spatial prediction. Herein, the intra prediction may meanintra-prediction,

When a prediction mode is an inter mode, the motion prediction unit 111may retrieve a region that best matches with an input block from areference image when performing motion prediction, and deduce a motionvector by using the retrieved region. In this case, a search region maybe used as the region. The reference image may be stored in thereference picture buffer 190. Here, when encoding/decoding for thereference image is performed, it may be stored in the reference picturebuffer 190.

The motion compensation unit 112 may generate a prediction block byperforming motion compensation for the current block using a motionvector. Herein, inter-prediction may mean inter-prediction or motioncompensation.

When the value of the motion vector is not an integer, the motionprediction unit 111 and the motion compensation unit 112 may generatethe prediction block by applying an interpolation filter to a partialregion of the reference picture. In order to perform inter-pictureprediction or motion compensation on a coding unit, it may be determinedthat which mode among a skip mode, a merge mode, an advanced motionvector prediction (AMVP) mode, and a current picture referring mode isused for motion prediction and motion compensation of a prediction unitincluded in the corresponding coding unit. Then, inter-pictureprediction or motion compensation may be differently performed dependingon the determined mode.

The subtractor 125 may generate a residual block by using a differenceof an input block and a prediction block. The residual block may becalled as a residual signal. The residual signal may mean a differencebetween an original signal and a prediction signal. In addition, theresidual signal may be a signal generated by transforming or quantizing,or transforming and quantizing a difference between the original signaland the prediction signal. The residual block may be a residual signalof a block unit.

The transform unit 130 may generate a transform coefficient byperforming transform of a residual block, and output the generatedtransform coefficient. Herein, the transform coefficient may be acoefficient value generated by performing transform of the residualblock. When a transform skip mode is applied, the transform unit 130 mayskip transform of the residual block.

A quantized level may be generated by applying quantization to thetransform coefficient or to the residual signal. Hereinafter, thequantized level may be also called as a transform coefficient inembodiments.

The quantization unit 140 may generate a quantized level by quantizingthe transform coefficient or the residual signal according to aparameter, and output the generated quantized level. Herein, thequantization unit 140 may quantize the transform coefficient by using aquantization matrix.

The entropy encoding unit 150 may generate a bitstream by performingentropy encoding according to a probability distribution on valuescalculated by the quantization unit 140 or on coding parameter valuescalculated when performing encoding, and output the generated bitstream.The entropy encoding unit 150 may perform entropy encoding of sampleinformation of an image and information for decoding an image. Forexample, the information for decoding the image may include a syntaxelement.

When entropy encoding is applied, symbols are represented so that asmaller number of bits are assigned to a symbol having a high chance ofbeing generated and a larger number of bits are assigned to a symbolhaving a low chance of being generated, and thus, the size of bit streamfor symbols to be encoded may be decreased. The entropy encoding unit150 may use an encoding method for entropy encoding such as exponentialGolomb, context-adaptive variable length coding (CAVLC),context-adaptive binary arithmetic coding (CABAC), etc. For example, theentropy encoding unit 150 may perform entropy encoding by using avariable length coding/code (VLC) table. In addition, the entropyencoding unit 150 may deduce a binarization method of a target symboland a probability model of a target symbol/bin, and perform arithmeticcoding by using the deduced binarization method, and a context model.

In order to encode a transform coefficient level (quantized level), theentropy encoding unit 150 may change a two-dimensional block formcoefficient into a one-dimensional vector form by using a transformcoefficient scanning method.

A coding parameter may include information (flag, index, etc.) such assyntax element that is encoded in an encoder and signaled to a decoder,and information derived when performing encoding or decoding. The codingparameter may mean information required when encoding or decoding animage. For example, at least one value or a combination form of aunit/block size, a unit/block depth, unit/block partition information,unit/block shape, unit/block partition structure, whether to partitionof a quad-tree form, whether to partition of a binary-tree form, apartition direction of a binary-tree form (horizontal direction orvertical direction), a partition form of a binary-tree form (symmetricpartition or asymmetric partition), whether or not a current coding unitis partitioned by ternary tree partitioning, direction (horizontal orvertical direction) of the ternary tree partitioning, type (symmetric orasymmetric type) of the ternary tree partitioning, whether a currentcoding unit is partitioned by multi-type tree partitioning, direction(horizontal or vertical direction) of the multi-type three partitioning,type (symmetric or asymmetric type) of the multi-type tree partitioning,and a tree (binary tree or ternary tree) structure of the multi-typetree partitioning, a prediction mode (intra prediction or interprediction), a luma intra-prediction mode/direction, a chromaintra-prediction mode/direction, intra partition information, interpartition information, a coding block partition flag, a prediction blockpartition flag, a transform block partition flag, a reference samplefiltering method, a reference sample filter tab, a reference samplefilter coefficient, a prediction block filtering method, a predictionblock filter tap, a prediction block filter coefficient, a predictionblock boundary filtering method, a prediction block boundary filter tab,a prediction block boundary filter coefficient, an intra-predictionmode, an inter-prediction mode, motion information, a motion vector, amotion vector difference, a reference picture index, a inter-predictionangle, an inter-prediction indicator, a prediction list utilizationflag, a reference picture list, a reference picture, a motion vectorpredictor index, a motion vector predictor candidate, a motion vectorcandidate list, whether to use a merge mode, a merge index, a mergecandidate, a merge candidate list, whether to use a skip mode, aninterpolation filter type, an interpolation filter tab, an interpolationfilter coefficient, a motion vector size, a presentation accuracy of amotion vector, a transform type, a transform size, information ofwhether or not a primary (first) transform is used, information ofwhether or not a secondary transform is used, a primary transform index,a secondary transform index, information of whether or not a residualsignal is present, a coded block pattern, a coded block flag (CBF), aquantization parameter, a quantization parameter residue, a quantizationmatrix, whether to apply an intra loop filter, an intra loop filtercoefficient, an intra loop filter tab, an intra loop filter shape/form,whether to apply a deblocking filter, a deblocking filter coefficient, adeblocking filter tab, a deblocking filter strength, a deblocking filtershape/form, whether to apply an adaptive sample offset, an adaptivesample offset value, an adaptive sample offset category, an adaptivesample offset type, whether to apply an adaptive loop filter, anadaptive loop filter coefficient, an adaptive loop filter tab, anadaptive loop filter shape/form, a binarization/inverse-binarizationmethod, a context model determining method, a context model updatingmethod, whether to perform a regular mode, whether to perform a bypassmode, a context bin, a bypass bin, a significant coefficient flag, alast significant coefficient flag, a coded flag for a unit of acoefficient group, a position of the last significant coefficient, aflag for whether a value of a coefficient is larger than 1, a flag forwhether a value of a coefficient is larger than 2, a flag for whether avalue of a coefficient is larger than 3, information on a remainingcoefficient value, a sign information, a reconstructed luma sample, areconstructed chroma sample, a residual luma sample, a residual chromasample, a luma transform coefficient, a chroma transform coefficient, aquantized luma level, a quantized chroma level, a transform coefficientlevel scanning method, a size of a motion vector search area at adecoder side, a shape of a motion vector search area at a decoder side,a number of time of a motion vector search at a decoder side,information on a CTU size, information on a minimum block size,information on a maximum block size, information on a maximum blockdepth, information on a minimum block depth, an imagedisplaying/outputting sequence, slice identification information, aslice type, slice partition information, tile identificationinformation, a tile type, tile partition information, tile groupidentification information, a tile group type, tile group partitioninformation, a picture type, a bit depth of an input sample, a bit depthof a reconstruction sample, a bit depth of a residual sample, a bitdepth of a transform coefficient, a bit depth of a quantized level, andinformation on a luma signal or information on a chroma signal may beincluded in the coding parameter.

Herein, signaling the flag or index may mean that a corresponding flagor index is entropy encoded and included in a bitstream by an encoder,and may mean that the corresponding flag or index is entropy decodedfrom a bitstream by a decoder.

When the encoding apparatus 100 performs encoding throughinter-prediction, an encoded current image may be used as a referenceimage for another image that is processed afterwards. Accordingly, theencoding apparatus 100 may reconstruct or decode the encoded currentimage, or store the reconstructed or decoded image as a reference imagein reference picture buffer 190.

A quantized level may be dequantized in the dequantization unit 160, ormay be inverse-transformed in the inverse-transform unit 170. Adequantized or inverse-transformed coefficient or both may be added witha prediction block by the adder 175. By adding the dequantized orinverse-transformed coefficient or both with the prediction block, areconstructed block may be generated. Herein, the dequantized orinverse-transformed coefficient or both may mean a coefficient on whichat least one of dequantization and inverse-transform is performed, andmay mean a reconstructed residual block.

A reconstructed block may pass through the filter unit 180. The filterunit 180 may apply at least one of a deblocking filter, a sampleadaptive offset (SAO), and an adaptive loop filter (ALF) to areconstructed sample, a reconstructed block or a reconstructed image.The filter unit 180 may be called as an in-loop filter.

The deblocking filter may remove block distortion generated inboundaries between blocks. In order to determine whether or not to applya deblocking filter, whether or not to apply a deblocking filter to acurrent block may be determined based samples included in several rowsor columns which are included in the block. When a deblocking filter isapplied to a block, another filter may be applied according to arequired deblocking filtering strength.

In order to compensate an encoding error, a proper offset value may beadded to a sample value by using a sample adaptive offset. The sampleadaptive offset may correct an offset of a deblocked image from anoriginal image by a sample unit. A method of partitioning samples of animage into a predetermined number of regions, determining a region towhich an offset is applied, and applying the offset to the determinedregion, or a method of applying an offset in consideration of edgeinformation on each sample may be used.

The adaptive loop filter may perform filtering based on a comparisonresult of the filtered reconstructed image and the original image.Samples included in an image may be partitioned into predeterminedgroups, a filter to be applied to each group may be determined, anddifferential filtering may be performed for each group. Information ofwhether or not to apply the ALF may be signaled by coding units (CUs),and a form and coefficient of the ALF to be applied to each block mayvary.

The reconstructed block or the reconstructed image having passed throughthe filter unit 180 may be stored in the reference picture buffer 190. Areconstructed block processed by the filter unit 180 may be a part of areference image. That is, a reference image is a reconstructed imagecomposed of reconstructed blocks processed by the filter unit 180. Thestored reference image may be used later in inter prediction or motioncompensation.

FIG. 2 is a block diagram showing a configuration of a decodingapparatus according to an embodiment and to which the present inventionis applied.

A decoding apparatus 200 may a decoder, a video decoding apparatus, oran image decoding apparatus.

Referring to FIG. 2 , the decoding apparatus 200 may include an entropydecoding unit 210, a dequantization unit 220, an inverse-transform unit230, an intra-prediction unit 240, a motion compensation unit 250, anadder 225, a filter unit 260, and a reference picture buffer 270.

The decoding apparatus 200 may receive a bitstream output from theencoding apparatus 100. The decoding apparatus 200 may receive abitstream stored in a computer readable recording medium, or may receivea bitstream that is streamed through a wired/wireless transmissionmedium. The decoding apparatus 200 may decode the bitstream by using anintra mode or an inter mode. In addition, the decoding apparatus 200 maygenerate a reconstructed image generated through decoding or a decodedimage, and output the reconstructed image or decoded image.

When a prediction mode used when decoding is an intra mode, a switch maybe switched to an intra. Alternatively, when a prediction mode used whendecoding is an inter mode, a switch may be switched to an inter mode.

The decoding apparatus 200 may obtain a reconstructed residual block bydecoding the input bitstream, and generate a prediction block. When thereconstructed residual block and the prediction block are obtained, thedecoding apparatus 200 may generate a reconstructed block that becomes adecoding target by adding the reconstructed residual block with theprediction block. The decoding target block may be called a currentblock.

The entropy decoding unit 210 may generate symbols by entropy decodingthe bitstream according to a probability distribution. The generatedsymbols may include a symbol of a quantized level form. Herein, anentropy decoding method may be an inverse-process of the entropyencoding method described above.

In order to decode a transform coefficient level (quantized level), theentropy decoding unit 210 may change a one-directional vector formcoefficient into a two-dimensional block form by using a transformcoefficient scanning method.

A quantized level may be dequantized in the dequantization unit 220, orinverse-transformed in the inverse-transform unit 230. The quantizedlevel may be a result of dequantizing or inverse-transforming or both,and may be generated as a reconstructed residual block. Herein, thedequantization unit 220 may apply a quantization matrix to the quantizedlevel.

When an intra mode is used, the intra-prediction unit 240 may generate aprediction block by performing, for the current block, spatialprediction that uses a sample value of a block adjacent to a decodingtarget block and which has been already decoded.

When an inter mode is used, the motion compensation unit 250 maygenerate a prediction block by performing, for the current block, motioncompensation that uses a motion vector and a reference image stored inthe reference picture buffer 270.

The adder 225 may generate a reconstructed block by adding thereconstructed residual block with the prediction block. The filter unit260 may apply at least one of a deblocking filter, a sample adaptiveoffset, and an adaptive loop filter to the reconstructed block orreconstructed image. The filter unit 260 may output the reconstructedimage. The reconstructed block or reconstructed image may be stored inthe reference picture buffer 270 and used when performinginter-prediction. A reconstructed block processed by the filter unit 260may be a part of a reference image. That is, a reference image is areconstructed image composed of reconstructed blocks processed by thefilter unit 260. The stored reference image may be used later in interprediction or motion compensation.

FIG. 3 is a view schematically showing a partition structure of an imagewhen encoding and decoding the image. FIG. 3 schematically shows anexample of partitioning a single unit into a plurality of lower units.

In order to efficiently partition an image, when encoding and decoding,a coding unit (CU) may be used. The coding unit may be used as a basicunit when encoding/decoding the image. In addition, the coding unit maybe used as a unit for distinguishing an intra prediction mode and aninter prediction mode when encoding/decoding the image. The coding unitmay be a basic unit used for prediction, transform, quantization,inverse-transform, dequantization, or an encoding/decoding process of atransform coefficient.

Referring to FIG. 3 , an image 300 is sequentially partitioned in alargest coding unit (LCU), and a LCU unit is determined as a partitionstructure. Herein, the LCU may be used in the same meaning as a codingtree unit (CTU). A unit partitioning may mean partitioning a blockassociated with to the unit. In block partition information, informationof a unit depth may be included. Depth information may represent anumber of times or a degree or both in which a unit is partitioned. Asingle unit may be partitioned into a plurality of lower level unitshierarchically associated with depth information based on a treestructure. In other words, a unit and a lower level unit generated bypartitioning the unit may correspond to a node and a child node of thenode, respectively. Each of partitioned lower unit may have depthinformation. Depth information may be information representing a size ofa CU, and may be stored in each CU. Unit depth represents times and/ordegrees related to partitioning a unit. Therefore, partitioninginformation of a lower-level unit may comprise information on a size ofthe lower-level unit.

A partition structure may mean a distribution of a coding unit (CU)within an LCU 310. Such a distribution may be determined according towhether or not to partition a single CU into a plurality (positiveinteger equal to or greater than 2 including 2, 4, 8, 16, etc.) of CUs.A horizontal size and a vertical size of the CU generated bypartitioning may respectively be half of a horizontal size and avertical size of the CU before partitioning, or may respectively havesizes smaller than a horizontal size and a vertical size beforepartitioning according to a number of times of partitioning. The CU maybe recursively partitioned into a plurality of CUs. By the recursivepartitioning, at least one among a height and a width of a CU afterpartitioning may decrease comparing with at least one among a height anda width of a CU before partitioning. Partitioning of the CU may berecursively performed until to a predefined depth or predefined size.For example, a depth of an LCU may be 0, and a depth of a smallestcoding unit (SCU) may be a predefined maximum depth. Herein, the LCU maybe a coding unit having a maximum coding unit size, and the SCU may be acoding unit having a minimum coding unit size as described above.Partitioning is started from the LCU 310, a CU depth increases by 1 as ahorizontal size or a vertical size or both of the CU decreases bypartitioning. For example, for each depth, a CU which is not partitionedmay have a size of 2N×2N. Also, in case of a CU which is partitioned, aCU with a size of 2N×2N may be partitioned into four CUs with a size ofN×N. A size of N may decrease to half as a depth increase by 1.

In addition, information whether or not the CU is partitioned may berepresented by using partition information of the CU. The partitioninformation may be 1-bit information. All CUs, except for a SCU, mayinclude partition information. For example, when a value of partitioninformation is a first value, the CU may not be partitioned, when avalue of partition information is a second value, the CU may bepartitioned.

Referring to FIG. 3 , an LCU having a depth 0 may be a 64×64 block. 0may be a minimum depth. A SCU having a depth 3 may be an 8×8 block. 3may be a maximum depth. A CU of a 32×32 block and a 16×16 block may berespectively represented as a depth 1 and a depth 2.

For example, when a single coding unit is partitioned into four codingunits, a horizontal size and a vertical size of the four partitionedcoding units may be a half size of a horizontal and vertical size of theCU before being partitioned. In one embodiment, when a coding unithaving a 32×32 size is partitioned into four coding units, each of thefour partitioned coding units may have a 16×16 size. When a singlecoding unit is partitioned into four coding units, it may be called thatthe coding unit may be partitioned into a quad-tree form.

For example, when one coding unit is partitioned into two sub-codingunits, the horizontal or vertical size (width or height) of each of thetwo sub-coding units may be half the horizontal or vertical size of theoriginal coding unit. For example, when a coding unit having a size of32×32 is vertically partitioned into two sub-coding units, each of thetwo sub-coding units may have a size of 16×32. For example, when acoding unit having a size of 8×32 is horizontally partitioned into twosub-coding units, each of the two sub-coding units may have a size of8×16. When one coding unit is partitioned into two sub-coding units, itcan be said that the coding unit is binary-partitioned or is partitionedby a binary tree partition structure.

For example, when one coding unit is partitioned into three sub-codingunits, the horizontal or vertical size of the coding unit can bepartitioned with a ratio of 1:2:1, thereby producing three sub-codingunits whose horizontal or vertical sizes are in a ratio of 1:2:1. Forexample, when a coding unit having a size of 16×32 is horizontallypartitioned into three sub-coding units, the three sub-coding units mayhave sizes of 16×8, 16×16, and 16×8 respectively, in the order from theuppermost to the lowermost sub-coding unit. For example, when a codingunit having a size of 32×32 is vertically split into three sub-codingunits, the three sub-coding units may have sizes of 8×32, 16×32, and8×32, respectively in the order from the left to the right sub-codingunit. When one coding unit is partitioned into three sub-coding units,it can be said that the coding unit is ternary-partitioned orpartitioned by a ternary tree partition structure.

In FIG. 3 , a coding tree unit (CTU) 320 is an example of a CTU to whicha quad tree partition structure, a binary tree partition structure, anda ternary tree partition structure are all applied.

As described above, in order to partition the CTU, at least one of aquad tree partition structure, a binary tree partition structure, and aternary tree partition structure may be applied. Various tree partitionstructures may be sequentially applied to the CTU, according to apredetermined priority order. For example, the quad tree partitionstructure may be preferentially applied to the CTU. A coding unit thatcannot be partitioned any longer using a quad tree partition structuremay correspond to a leaf node of a quad tree. A coding unitcorresponding to a leaf node of a quad tree may serve as a root node ofa binary and/or ternary tree partition structure. That is, a coding unitcorresponding to a leaf node of a quad tree may be further partitionedby a binary tree partition structure or a ternary tree partitionstructure, or may not be further partitioned. Therefore, by preventing acoding block that results from binary tree partitioning or ternary treepartitioning of a coding unit corresponding to a leaf node of a quadtree from undergoing further quad tree partitioning, block partitioningand/or signaling of partition information can be effectively performed.

The fact that a coding unit corresponding to a node of a quad tree ispartitioned may be signaled using quad partition information. The quadpartition information having a first value (e.g., “1”) may indicate thata current coding unit is partitioned by the quad tree partitionstructure. The quad partition information having a second value (e.g.,“0”) may indicate that a current coding unit is not partitioned by thequad tree partition structure. The quad partition information may be aflag having a predetermined length (e.g., one bit).

There may not be a priority between the binary tree partitioning and theternary tree partitioning. That is, a coding unit corresponding to aleaf node of a quad tree may further undergo arbitrary partitioningamong the binary tree partitioning and the ternary tree partitioning. Inaddition, a coding unit generated through the binary tree partitioningor the ternary tree partitioning may undergo a further binary treepartitioning or a further ternary tree partitioning, or may not befurther partitioned.

A tree structure in which there is no priority among the binary treepartitioning and the ternary tree partitioning is referred to as amulti-type tree structure. A coding unit corresponding to a leaf node ofa quad tree may serve as a root node of a multi-type tree. Whether topartition a coding unit which corresponds to a node of a multi-type treemay be signaled using at least one of multi-type tree partitionindication information, partition direction information, and partitiontree information. For partitioning of a coding unit corresponding to anode of a multi-type tree, the multi-type tree partition indicationinformation, the partition direction, and the partition tree informationmay be sequentially signaled.

The multi-type tree partition indication information having a firstvalue (e.g., “1”) may indicate that a current coding unit is to undergoa multi-type tree partitioning. The multi-type tree partition indicationinformation having a second value (e.g., “0”) may indicate that acurrent coding unit is not to undergo a multi-type tree partitioning.

When a coding unit corresponding to a node of a multi-type tree isfurther partitioned by a multi-type tree partition structure, the codingunit may include partition direction information. The partitiondirection information may indicate in which direction a current codingunit is to be partitioned for the multi-type tree partitioning. Thepartition direction information having a first value (e.g., “1”) mayindicate that a current coding unit is to be vertically partitioned. Thepartition direction information having a second value (e.g., “0”) mayindicate that a current coding unit is to be horizontally partitioned.

When a coding unit corresponding to a node of a multi-type tree isfurther partitioned by a multi-type tree partition structure, thecurrent coding unit may include partition tree information. Thepartition tree information may indicate a tree partition structure whichis to be used for partitioning of a node of a multi-type tree. Thepartition tree information having a first value (e.g., “1”) may indicatethat a current coding unit is to be partitioned by a binary treepartition structure. The partition tree information having a secondvalue (e.g., “0”) may indicate that a current coding unit is to bepartitioned by a ternary tree partition structure.

The partition indication information, the partition tree information,and the partition direction information may each be a flag having apredetermined length (e.g., one bit).

At least any one of the quadtree partition indication information, themulti-type tree partition indication information, the partitiondirection information, and the partition tree information may be entropyencoded/decoded. For the entropy-encoding/decoding of those types ofinformation, information on a neighboring coding unit adjacent to thecurrent coding unit may be used. For example, there is a highprobability that the partition type (the partitioned or non-partitioned,the partition tree, and/or the partition direction) of a leftneighboring coding unit and/or an upper neighboring coding unit of acurrent coding unit is similar to that of the current coding unit.Therefore, context information for entropy encoding/decoding of theinformation on the current coding unit may be derived from theinformation on the neighboring coding units. The information on theneighboring coding units may include at least any one of quad partitioninformation, multi-type tree partition indication information, partitiondirection information, and partition tree information.

As another example, among binary tree partitioning and ternary treepartitioning, binary tree partitioning may be preferentially performed.That is, a current coding unit may primarily undergo binary treepartitioning, and then a coding unit corresponding to a leaf node of abinary tree may be set as a root node for ternary tree partitioning. Inthis case, neither quad tree partitioning nor binary tree partitioningmay not be performed on the coding unit corresponding to a node of aternary tree.

A coding unit that cannot be partitioned by a quad tree partitionstructure, a binary tree partition structure, and/or a ternary treepartition structure becomes a basic unit for coding, prediction and/ortransformation. That is, the coding unit cannot be further partitionedfor prediction and/or transformation. Therefore, the partition structureinformation and the partition information used for partitioning a codingunit into prediction units and/or transformation units may not bepresent in a bit stream.

However, when the size of a coding unit (i.e., a basic unit forpartitioning) is larger than the size of a maximum transformation block,the coding unit may be recursively partitioned until the size of thecoding unit is reduced to be equal to or smaller than the size of themaximum transformation block. For example, when the size of a codingunit is 64×64 and when the size of a maximum transformation block is32×32, the coding unit may be partitioned into four 32×32 blocks fortransformation. For example, when the size of a coding unit is 32×64 andthe size of a maximum transformation block is 32×32, the coding unit maybe partitioned into two 32×32 blocks for the transformation. In thiscase, the partitioning of the coding unit for transformation is notsignaled separately, and may be determined through comparison betweenthe horizontal or vertical size of the coding unit and the horizontal orvertical size of the maximum transformation block. For example, when thehorizontal size (width) of the coding unit is larger than the horizontalsize (width) of the maximum transformation block, the coding unit may bevertically bisected. For example, when the vertical size (height) of thecoding unit is larger than the vertical size (height) of the maximumtransformation block, the coding unit may be horizontally bisected.

Information of the maximum and/or minimum size of the coding unit andinformation of the maximum and/or minimum size of the transformationblock may be signaled or determined at an upper level of the codingunit. The upper level may be, for example, a sequence level, a picturelevel, a slice level, a tile group level, a tile level, or the like. Forexample, the minimum size of the coding unit may be determined to be4×4. For example, the maximum size of the transformation block may bedetermined to be 64×64. For example, the minimum size of thetransformation block may be determined to be 4×4. Information of theminimum size (quad tree minimum size) of a coding unit corresponding toa leaf node of a quad tree and/or information of the maximum depth (themaximum tree depth of a multi-type tree) from a root node to a leaf nodeof the multi-type tree may be signaled or determined at an upper levelof the coding unit. For example, the upper level may be a sequencelevel, a picture level, a slice level, a tile group level, a tile level,or the like. Information of the minimum size of a quad tree and/orinformation of the maximum depth of a multi-type tree may be signaled ordetermined for each of an intra-picture slice and an inter-pictureslice.

Difference information between the size of a CTU and the maximum size ofa transformation block may be signaled or determined at an upper levelof the coding unit. For example, the upper level may be a sequencelevel, a picture level, a slice level, a tile group level, a tile level,or the like. Information of the maximum size of the coding unitscorresponding to the respective nodes of a binary tree (hereinafter,referred to as a maximum size of a binary tree) may be determined basedon the size of the coding tree unit and the difference information. Themaximum size of the coding units corresponding to the respective nodesof a ternary tree (hereinafter, referred to as a maximum size of aternary tree) may vary depending on the type of slice. For example, foran intra-picture slice, the maximum size of a ternary tree may be 32×32.For example, for an inter-picture slice, the maximum size of a ternarytree may be 128×128. For example, the minimum size of the coding unitscorresponding to the respective nodes of a binary tree (hereinafter,referred to as a minimum size of a binary tree) and/or the minimum sizeof the coding units corresponding to the respective nodes of a ternarytree (hereinafter, referred to as a minimum size of a ternary tree) maybe set as the minimum size of a coding block.

As another example, the maximum size of a binary tree and/or the maximumsize of a ternary tree may be signaled or determined at the slice level.Alternatively, the minimum size of the binary tree and/or the minimumsize of the ternary tree may be signaled or determined at the slicelevel.

Depending on size and depth information of the above-described variousblocks, quad partition information, multi-type tree partition indicationinformation, partition tree information and/or partition directioninformation may be included or may not be included in a bit stream.

For example, when the size of the coding unit is not larger than theminimum size of a quad tree, the coding unit does not contain quadpartition information. Thus, the quad partition information may bededuced from a second value.

For example, when the sizes (horizontal and vertical sizes) of a codingunit corresponding to a node of a multi-type tree are larger than themaximum sizes (horizontal and vertical sizes) of a binary tree and/orthe maximum sizes (horizontal and vertical sizes) of a ternary tree, thecoding unit may not be binary-partitioned or ternary-partitioned.Accordingly, the multi-type tree partition indication information maynot be signaled but may be deduced from a second value.

Alternatively, when the sizes (horizontal and vertical sizes) of acoding unit corresponding to a node of a multi-type tree are the same asthe maximum sizes (horizontal and vertical sizes) of a binary treeand/or are two times as large as the maximum sizes (horizontal andvertical sizes) of a ternary tree, the coding unit may not be furtherbinary-partitioned or ternary-partitioned. Accordingly, the multi-typetree partition indication information may not be signaled but be derivedfrom a second value. This is because when a coding unit is partitionedby a binary tree partition structure and/or a ternary tree partitionstructure, a coding unit smaller than the minimum size of a binary treeand/or the minimum size of a ternary tree is generated.

Alternatively, the binary tree partitioning or the ternary treepartitioning may be limited on the basis of the size of a virtualpipeline data unit (hereinafter, a pipeline buffer size). For example,when the coding unit is divided into sub-coding units which do not fitthe pipeline buffer size by the binary tree partitioning or the ternarytree partitioning, the corresponding binary tree partitioning or ternarytree partitioning may be limited. The pipeline buffer size may be thesize of the maximum transform block (e.g., 64×64). For example, when thepipeline buffer size is 64×64, the division below may be limited.

-   -   N×M (N and/or M is 128) Ternary tree partitioning for coding        units    -   128×N (N<=64) Binary tree partitioning in horizontal direction        for coding units    -   N×128 (N<=64) Binary tree partitioning in vertical direction for        coding units

Alternatively, when the depth of a coding unit corresponding to a nodeof a multi-type tree is equal to the maximum depth of the multi-typetree, the coding unit may not be further binary-partitioned and/orternary-partitioned. Accordingly, the multi-type tree partitionindication information may not be signaled but may be deduced from asecond value.

Alternatively, only when at least one of vertical direction binary treepartitioning, horizontal direction binary tree partitioning, verticaldirection ternary tree partitioning, and horizontal direction ternarytree partitioning is possible for a coding unit corresponding to a nodeof a multi-type tree, the multi-type tree partition indicationinformation may be signaled. Otherwise, the coding unit may not bebinary-partitioned and/or ternary-partitioned. Accordingly, themulti-type tree partition indication information may not be signaled butmay be deduced from a second value.

Alternatively, only when both of the vertical direction binary treepartitioning and the horizontal direction binary tree partitioning orboth of the vertical direction ternary tree partitioning and thehorizontal direction ternary tree partitioning are possible for a codingunit corresponding to a node of a multi-type tree, the partitiondirection information may be signaled. Otherwise, the partitiondirection information may not be signaled but may be derived from avalue indicating possible partitioning directions.

Alternatively, only when both of the vertical direction binary treepartitioning and the vertical direction ternary tree partitioning orboth of the horizontal direction binary tree partitioning and thehorizontal direction ternary tree partitioning are possible for a codingtree corresponding to a node of a multi-type tree, the partition treeinformation may be signaled. Otherwise, the partition tree informationmay not be signaled but be deduced from a value indicating a possiblepartitioning tree structure.

FIG. 4 is a view showing an intra-prediction process.

Arrows from center to outside in FIG. 4 may represent predictiondirections of intra prediction modes.

Intra encoding and/or decoding may be performed by using a referencesample of a neighbor block of the current block. A neighbor block may bea reconstructed neighbor block. For example, intra encoding and/ordecoding may be performed by using a coding parameter or a value of areference sample included in a reconstructed neighbor block.

A prediction block may mean a block generated by performing intraprediction. A prediction block may correspond to at least one among CU,PU and TU. A unit of a prediction block may have a size of one among CU,PU and TU. A prediction block may be a square block having a size of2×2, 4×4, 16×16, 32×32 or 64×64 etc. or may be a rectangular blockhaving a size of 2×8, 4×8, 2×16, 4×16 and 8×16 etc.

Intra prediction may be performed according to intra prediction mode forthe current block. The number of intra prediction modes which thecurrent block may have may be a fixed value and may be a valuedetermined differently according to an attribute of a prediction block.For example, an attribute of a prediction block may comprise a size of aprediction block and a shape of a prediction block, etc.

The number of intra-prediction modes may be fixed to N regardless of ablock size. Or, the number of intra prediction modes may be 3, 5, 9, 17,34, 35, 36, 65, or 67 etc. Alternatively, the number of intra-predictionmodes may vary according to a block size or a color component type orboth. For example, the number of intra prediction modes may varyaccording to whether the color component is a luma signal or a chromasignal. For example, as a block size becomes large, a number ofintra-prediction modes may increase. Alternatively, a number ofintra-prediction modes of a luma component block may be larger than anumber of intra-prediction modes of a chroma component block.

An intra-prediction mode may be a non-angular mode or an angular mode.The non-angular mode may be a DC mode or a planar mode, and the angularmode may be a prediction mode having a specific direction or angle. Theintra-prediction mode may be expressed by at least one of a mode number,a mode value, a mode numeral, a mode angle, and mode direction. A numberof intra-prediction modes may be M, which is larger than 1, includingthe non-angular and the angular mode. In order to intra-predict acurrent block, a step of determining whether or not samples included ina reconstructed neighbor block may be used as reference samples of thecurrent block may be performed. When a sample that is not usable as areference sample of the current block is present, a value obtained byduplicating or performing interpolation on at least one sample valueamong samples included in the reconstructed neighbor block or both maybe used to replace with a non-usable sample value of a sample, thus thereplaced sample value is used as a reference sample of the currentblock.

FIG. 7 is a diagram illustrating reference samples capable of being usedfor intra prediction.

As shown in FIG. 7 , at least one of the reference sample line 0 to thereference sample line 3 may be used for intra prediction of the currentblock. In FIG. 7 , the samples of a segment A and a segment F may bepadded with the samples closest to a segment B and a segment E,respectively, instead of retrieving from the reconstructed neighboringblock. Index information indicating the reference sample line to be usedfor intra prediction of the current block may be signaled. When theupper boundary of the current block is the boundary of the CTU, only thereference sample line 0 may be available. Therefore, in this case, theindex information may not be signaled. When a reference sample lineother than the reference sample line 0 is used, filtering for aprediction block, which will be described later, may not be performed.

When intra-predicting, a filter may be applied to at least one of areference sample and a prediction sample based on an intra-predictionmode and a current block size.

In case of a planar mode, when generating a prediction block of acurrent block, according to a position of a prediction target samplewithin a prediction block, a sample value of the prediction targetsample may be generated by using a weighted sum of an upper and leftside reference sample of a current sample, and a right upper side andleft lower side reference sample of the current block. In addition, incase of a DC mode, when generating a prediction block of a currentblock, an average value of upper side and left side reference samples ofthe current block may be used. In addition, in case of an angular mode,a prediction block may be generated by using an upper side, a left side,a right upper side, and/or a left lower side reference sample of thecurrent block. In order to generate a prediction sample value,interpolation of a real number unit may be performed.

In the case of intra prediction between color components, a predictionblock for the current block of the second color component may begenerated on the basis of the corresponding reconstructed block of thefirst color component. For example, the first color component may be aluma component, and the second color component may be a chromacomponent. For intra prediction between color components, the parametersof the linear model between the first color component and the secondcolor component may be derived on the basis of the template. Thetemplate may include upper and/or left neighboring samples of thecurrent block and upper and/or left neighboring samples of thereconstructed block of the first color component corresponding thereto.For example, the parameters of the linear model may be derived using asample value of a first color component having a maximum value amongsamples in a template and a sample value of a second color componentcorresponding thereto, and a sample value of a first color componenthaving a minimum value among samples in the template and a sample valueof a second color component corresponding thereto. When the parametersof the linear model are derived, a corresponding reconstructed block maybe applied to the linear model to generate a prediction block for thecurrent block. According to a video format, subsampling may be performedon the neighboring samples of the reconstructed block of the first colorcomponent and the corresponding reconstructed block. For example, whenone sample of the second color component corresponds to four samples ofthe first color component, four samples of the first color component maybe sub-sampled to compute one corresponding sample. In this case, theparameter derivation of the linear model and intra prediction betweencolor components may be performed on the basis of the correspondingsub-sampled samples. Whether or not to perform intra prediction betweencolor components and/or the range of the template may be signaled as theintra prediction mode.

The current block may be partitioned into two or four sub-blocks in thehorizontal or vertical direction. The partitioned sub-blocks may besequentially reconstructed. That is, the intra prediction may beperformed on the sub-block to generate the sub-prediction block. Inaddition, dequantization and/or inverse transform may be performed onthe sub-blocks to generate sub-residual blocks. A reconstructedsub-block may be generated by adding the sub-prediction block to thesub-residual block. The reconstructed sub-block may be used as areference sample for intra prediction of the sub-sub-blocks. Thesub-block may be a block including a predetermined number (for example,16) or more samples. Accordingly, for example, when the current block isan 8×4 block or a 4×8 block, the current block may be partitioned intotwo sub-blocks. Also, when the current block is a 4×4 block, the currentblock may not be partitioned into sub-blocks. When the current block hasother sizes, the current block may be partitioned into four sub-blocks.Information on whether or not to perform the intra prediction based onthe sub-blocks and/or the partitioning direction (horizontal orvertical) may be signaled. The intra prediction based on the sub-blocksmay be limited to be performed only when reference sample line 0 isused. When the intra prediction based on the sub-block is performed,filtering for the prediction block, which will be described later, maynot be performed.

The final prediction block may be generated by performing filtering onthe prediction block that is intra-predicted. The filtering may beperformed by applying predetermined weights to the filtering targetsample, the left reference sample, the upper reference sample, and/orthe upper left reference sample. The weight and/or the reference sample(range, position, etc.) used for the filtering may be determined on thebasis of at least one of a block size, an intra prediction mode, and aposition of the filtering target sample in the prediction block. Thefiltering may be performed only in the case of a predetermined intraprediction mode (e.g., DC, planar, vertical, horizontal, diagonal,and/or adjacent diagonal modes). The adjacent diagonal mode may be amode in which k is added to or subtracted from the diagonal mode. Forexample, k may be a positive integer of 8 or less.

An intra-prediction mode of a current block may be entropyencoded/decoded by predicting an intra-prediction mode of a blockpresent adjacent to the current block. When intra-prediction modes ofthe current block and the neighbor block are identical, information thatthe intra-prediction modes of the current block and the neighbor blockare identical may be signaled by using predetermined flag information.In addition, indicator information of an intra-prediction mode that isidentical to the intra-prediction mode of the current block amongintra-prediction modes of a plurality of neighbor blocks may besignaled. When intra-prediction modes of the current block and theneighbor block are different, intra-prediction mode information of thecurrent block may be entropy encoded/decoded by performing entropyencoding/decoding based on the intra-prediction mode of the neighborblock.

FIG. 5 is a diagram illustrating an embodiment of an inter-pictureprediction process.

In FIG. 5 , a rectangle may represent a picture. In FIG. 5 , an arrowrepresents a prediction direction. Pictures may be categorized intointra pictures (I pictures), predictive pictures (P pictures), andBi-predictive pictures (B pictures) according to the encoding typethereof.

The I picture may be encoded through intra-prediction without requiringinter-picture prediction. The P picture may be encoded throughinter-picture prediction by using a reference picture that is present inone direction (i.e., forward direction or backward direction) withrespect to a current block. The B picture may be encoded throughinter-picture prediction by using reference pictures that are preset intwo directions (i.e., forward direction and backward direction) withrespect to a current block. When the inter-picture prediction is used,the encoder may perform inter-picture prediction or motion compensationand the decoder may perform the corresponding motion compensation.

Hereinbelow, an embodiment of the inter-picture prediction will bedescribed in detail.

The inter-picture prediction or motion compensation may be performedusing a reference picture and motion information.

Motion information of a current block may be derived duringinter-picture prediction by each of the encoding apparatus 100 and thedecoding apparatus 200. The motion information of the current block maybe derived by using motion information of a reconstructed neighboringblock, motion information of a collocated block (also referred to as acol block or a co-located block), and/or a block adjacent to theco-located block. The co-located block may mean a block that is locatedspatially at the same position as the current block, within a previouslyreconstructed collocated picture (also referred to as a col picture or aco-located picture). The co-located picture may be one picture among oneor more reference pictures included in a reference picture list.

The derivation method of the motion information may be differentdepending on the prediction mode of the current block. For example, aprediction mode applied for inter prediction includes an AMVP mode, amerge mode, a skip mode, a merge mode with a motion vector difference, asubblock merge mode, a triangle partition mode, an combined inter intraprediction mode, affine mode, and the like. Herein, the merge mode maybe referred to as a motion merge mode.

For example, when the AMVP is used as the prediction mode, at least oneof motion vectors of the reconstructed neighboring blocks, motionvectors of the co-located blocks, motion vectors of blocks adjacent tothe co-located blocks, and a (0, 0) motion vector may be determined asmotion vector candidates for the current block, and a motion vectorcandidate list is generated by using the emotion vector candidates. Themotion vector candidate of the current block can be derived by using thegenerated motion vector candidate list. The motion information of thecurrent block may be determined based on the derived motion vectorcandidate. The motion vectors of the collocated blocks or the motionvectors of the blocks adjacent to the collocated blocks may be referredto as temporal motion vector candidates, and the motion vectors of thereconstructed neighboring blocks may be referred to as spatial motionvector candidates.

The encoding apparatus 100 may calculate a motion vector difference(MVD) between the motion vector of the current block and the motionvector candidate and may perform entropy encoding on the motion vectordifference (MVD). In addition, the encoding apparatus 100 may performentropy encoding on a motion vector candidate index and generate abitstream. The motion vector candidate index may indicate an optimummotion vector candidate among the motion vector candidates included inthe motion vector candidate list. The decoding apparatus may performentropy decoding on the motion vector candidate index included in thebitstream and may select a motion vector candidate of a decoding targetblock from among the motion vector candidates included in the motionvector candidate list by using the entropy-decoded motion vectorcandidate index. In addition, the decoding apparatus 200 may add theentropy-decoded MVD and the motion vector candidate extracted throughthe entropy decoding, thereby deriving the motion vector of the decodingtarget block.

Meanwhile, the coding apparatus 100 may perform entropy-coding onresolution information of the calculated MVD. The decoding apparatus 200may adjust the resolution of the entropy-decoded MVD using the MVDresolution information.

Meanwhile, the coding apparatus 100 calculates a motion vectordifference (MVD) between a motion vector and a motion vector candidatein the current block on the basis of an affine model, and performsentropy-coding on the MVD. The decoding apparatus 200 derives a motionvector on a per sub-block basis by deriving an affine control motionvector of a decoding target block through the sum of the entropy-decodedMVD and an affine control motion vector candidate.

The bitstream may include a reference picture index indicating areference picture. The reference picture index may be entropy-encoded bythe encoding apparatus 100 and then signaled as a bitstream to thedecoding apparatus 200. The decoding apparatus 200 may generate aprediction block of the decoding target block based on the derivedmotion vector and the reference picture index information.

Another example of the method of deriving the motion information of thecurrent may be the merge mode. The merge mode may mean a method ofmerging motion of a plurality of blocks. The merge mode may mean a modeof deriving the motion information of the current block from the motioninformation of the neighboring blocks. When the merge mode is applied,the merge candidate list may be generated using the motion informationof the reconstructed neighboring blocks and/or the motion information ofthe collocated blocks. The motion information may include at least oneof a motion vector, a reference picture index, and an inter-pictureprediction indicator. The prediction indicator may indicateone-direction prediction (L0 prediction or L1 prediction) ortwo-direction predictions (L0 prediction and L1 prediction).

The merge candidate list may be a list of motion information stored. Themotion information included in the merge candidate list may be at leastone of motion information (spatial merge candidate) of a neighboringblock adjacent to the current block, motion information (temporal mergecandidate) of the collocated block of the current block in the referencepicture, new motion information generated by a combination of the motioninformation exiting in the merge candidate list, motion information(history-based merge candidate) of the block that is encoded/decodedbefore the current block, and zero merge candidate.

The encoding apparatus 100 may generate a bitstream by performingentropy encoding on at least one of a merge flag and a merge index andmay signal the bitstream to the decoding apparatus 200. The merge flagmay be information indicating whether or not to perform the merge modefor each block, and the merge index may be information indicating thatwhich neighboring block, among the neighboring blocks of the currentblock, is a merge target block. For example, the neighboring blocks ofthe current block may include a left neighboring block on the left ofthe current block, an upper neighboring block disposed above the currentblock, and a temporal neighboring block temporally adjacent to thecurrent block.

Meanwhile, the coding apparatus 100 performs entropy-coding on thecorrection information for correcting the motion vector among the motioninformation of the merge candidate and signals the same to the decodingapparatus 200. The decoding apparatus 200 can correct the motion vectorof the merge candidate selected by the merge index on the basis of thecorrection information. Here, the correction information may include atleast one of information on whether or not to perform the correction,correction direction information, and correction size information. Asdescribed above, the prediction mode that corrects the motion vector ofthe merge candidate on the basis of the signaled correction informationmay be referred to as a merge mode having the motion vector difference.

The skip mode may be a mode in which the motion information of theneighboring block is applied to the current block as it is. When theskip mode is applied, the encoding apparatus 100 may perform entropyencoding on information of the fact that the motion information of whichblock is to be used as the motion information of the current block togenerate a bit stream, and may signal the bitstream to the decodingapparatus 200. The encoding apparatus 100 may not signal a syntaxelement regarding at least any one of the motion vector differenceinformation, the encoding block flag, and the transform coefficientlevel to the decoding apparatus 200.

The subblock merge mode may mean a mode that derives the motioninformation in units of sub-blocks of a coding block (CU). When thesubblock merge mode is applied, a subblock merge candidate list may begenerated using motion information (sub-block based temporal mergecandidate) of the sub-block collocated to the current sub-block in thereference image and/or an affine control point motion vector mergecandidate.

The triangle partition mode may mean a mode that derives motioninformation by partitioning the current block into diagonal directions,derives each prediction sample using each of the derived motioninformation, and derives the prediction sample of the current block byweighting each of the derived prediction samples.

The inter-intra combined prediction mode may mean a mode that derives aprediction sample of the current block by weighting a prediction samplegenerated by inter prediction and a prediction sample generated by intraprediction.

The decoding apparatus 200 may correct the derived motion information byitself. The decoding apparatus 200 may search the predetermined regionon the basis of the reference block indicated by the derived motioninformation and derive the motion information having the minimum SAD asthe corrected motion information.

The decoding apparatus 200 may compensate a prediction sample derivedvia inter prediction using an optical flow.

FIG. 6 is a diagram illustrating a transform and quantization process.

As illustrated in FIG. 6 , a transform and/or quantization process isperformed on a residual signal to generate a quantized level signal. Theresidual signal is a difference between an original block and aprediction block (i.e., an intra prediction block or an inter predictionblock). The prediction block is a block generated through intraprediction or inter prediction. The transform may be a primarytransform, a secondary transform, or both. The primary transform of theresidual signal results in transform coefficients, and the secondarytransform of the transform coefficients results in secondary transformcoefficients.

At least one scheme selected from among various transform schemes whichare preliminarily defined is used to perform the primary transform. Forexample, examples of the predefined transform schemes include discretecosine transform (DCT), discrete sine transform (DST), andKarhunen-Loève transform (KLT). The transform coefficients generatedthrough the primary transform may undergo the secondary transform. Thetransform schemes used for the primary transform and/or the secondarytransform may be determined according to coding parameters of thecurrent block and/or neighboring blocks of the current block.Alternatively, transform information indicating the transform scheme maybe signaled. The DCT-based transform may include, for example, DCT-2,DCT-8, and the like. The DST-based transform may include, for example,DST-7.

A quantized-level signal (quantization coefficients) may be generated byperforming quantization on the residual signal or a result of performingthe primary transform and/or the secondary transform. The quantizedlevel signal may be scanned according to at least one of a diagonalup-right scan, a vertical scan, and a horizontal scan, depending on anintra prediction mode of a block or a block size/shape. For example, asthe coefficients are scanned in a diagonal up-right scan, thecoefficients in a block form change into a one-dimensional vector form.Aside from the diagonal up-right scan, the horizontal scan ofhorizontally scanning a two-dimensional block form of coefficients orthe vertical scan of vertically scanning a two-dimensional block form ofcoefficients may be used depending on the intra prediction mode and/orthe size of a transform block. The scanned quantized-level coefficientsmay be entropy-encoded to be inserted into a bitstream.

A decoder entropy-decodes the bitstream to obtain the quantized-levelcoefficients. The quantized-level coefficients may be arranged in atwo-dimensional block form through inverse scanning. For the inversescanning, at least one of a diagonal up-right scan, a vertical scan, anda horizontal scan may be used.

The quantized-level coefficients may then be dequantized, then besecondary-inverse-transformed as necessary, and finally beprimary-inverse-transformed as necessary to generate a reconstructedresidual signal.

Inverse mapping in a dynamic range may be performed for a luma componentreconstructed through intra prediction or inter prediction beforein-loop filtering. The dynamic range may be divided into 16 equal piecesand the mapping function for each piece may be signaled. The mappingfunction may be signaled at a slice level or a tile group level. Aninverse mapping function for performing the inverse mapping may bederived on the basis of the mapping function. In-loop filtering,reference picture storage, and motion compensation are performed in aninverse mapped region, and a prediction block generated through interprediction is converted into a mapped region via mapping using themapping function, and then used for generating the reconstructed block.However, since the intra prediction is performed in the mapped region,the prediction block generated via the intra prediction may be used forgenerating the reconstructed block without mapping/inverse mapping.

When the current block is a residual block of a chroma component, theresidual block may be converted into an inverse mapped region byperforming scaling on the chroma component of the mapped region. Theavailability of the scaling may be signaled at the slice level or thetile group level. The scaling may be applied only when the mapping forthe luma component is available and the division of the luma componentand the division of the chroma component follow the same tree structure.The scaling may be performed on the basis of an average of sample valuesof a luma prediction block corresponding to the color difference block.In this case, when the current block uses inter prediction, the lumaprediction block may mean a mapped luma prediction block. A valuenecessary for the scaling may be derived by referring to a lookup tableusing an index of a piece to which an average of sample values of a lumaprediction block belongs. Finally, by scaling the residual block usingthe derived value, the residual block may be switched to the inversemapped region. Then, chroma component block restoration, intraprediction, inter prediction, in-loop filtering, and reference picturestorage may be performed in the inverse mapped area.

Information indicating whether the mapping/inverse mapping of the lumacomponent and chroma component is available may be signaled through aset of sequence parameters.

The prediction block of the current block may be generated on the basisof a block vector indicating a displacement between the current blockand the reference block in the current picture. In this way, aprediction mode for generating a prediction block with reference to thecurrent picture is referred to as an intra block copy (IBC) mode. TheIBC mode may be applied to M×N (M<=64, N<=64) coding units. The IBC modemay include a skip mode, a merge mode, an AMVP mode, and the like. Inthe case of a skip mode or a merge mode, a merge candidate list isconstructed, and the merge index is signaled so that one merge candidatemay be specified. The block vector of the specified merge candidate maybe used as a block vector of the current block. The merge candidate listmay include at least one of a spatial candidate, a history-basedcandidate, a candidate based on an average of two candidates, and azero-merge candidate. In the case of an AMVP mode, the difference blockvector may be signaled. In addition, the prediction block vector may bederived from the left neighboring block and the upper neighboring blockof the current block. The index on which neighboring block to use may besignaled. The prediction block in the IBC mode is included in thecurrent CTU or the left CTU and limited to a block in the alreadyreconstructed area. For example, a value of the block vector may belimited such that the prediction block of the current block ispositioned in an area of three 64×64 blocks preceding the 64×64 block towhich the current block belongs in the coding/decoding order. Bylimiting the value of the block vector in this way, memory consumptionand device complexity according to the IBC mode implementation may bereduced.

Hereinafter, the embodiments of the present invention will be describedin detail with reference to FIGS. 8 to 18 .

In this specification, “intra prediction and inter prediction”, “interprediction and intra prediction” or “combined inter intra prediction”means combined inter intra prediction (CIIP) and may mean a mode forderiving a prediction sample of a current block by weighted-summing aprediction sample generated by inter prediction and a prediction samplegenerated by intra prediction. Combined inter intra prediction may beperformed in coding units (CUs), coding block units, prediction units,prediction block units, transform units, transform blocks, subblockunits of a coding unit, subblock units of a coding block, subblock unitsof a prediction unit, subblock units of a prediction block, subblockunits of a transform unit or subblock units of a transform block.

In combined inter intra prediction, filtering is applied to each of aprediction sample generated by intra prediction and a prediction samplegenerated by inter prediction.

For example, filtering based on a sample location is applicable to ablock generated by intra prediction.

For example, filtering based on a sample location is applicable to ablock generated by inter prediction.

A weight used in the weighted sum of the combined inter intra predictionmay vary according to information on a current block, information on aneighbor block, a quantization parameter (QP), etc. At this time, theinformation on the current/neighbor block may mean the width of thecurrent/neighbor block, the height of the current/neighbor block, theratio of the width to the height of the current/neighbor block, thelocation of the current/neighbor block, the prediction mode of thecurrent/neighbor block, the intra prediction mode of thecurrent/neighbor block, the inter prediction mode of thecurrent/neighbor block, the weight of the neighbor block, etc., at leastone of which may be used to determine the weight. Here, the informationon the current block and the information on the neighbor block may meanthe coding parameter of the current block and the coding parameter ofthe neighbor block.

The weight applied to the intra prediction block in the combined interintra prediction may be determined based on the coding parameter relatedto the intra prediction of the current block. In addition, the weightapplied to the inter prediction block in the combined inter intraprediction may be determined based on the coding parameter related tothe inter prediction of the current block.

Meanwhile, the weight applied to the intra prediction block in thecombined inter intra prediction may be determined based on the codingparameter related to the intra prediction of the neighbor block. Inaddition, the weight applied to the intra prediction block in thecombined inter intra prediction may be determined based on the codingparameter related to the inter prediction of the neighbor block.

When the prediction block of the current block is generated throughcombined inter intra prediction, the current block may be regarded asusing the inter prediction mode. In at least one of transform/inversetransform, quantization/dequantization, entropy encoding/decoding,deblocking filtering, adaptive sample offset or adaptive in-loopfiltering, the current block may be regarded as being in an interprediction mode and may be processed.

Combined inter intra prediction is applicable to at least one of a lumablock or a chroma block.

Combined inter intra prediction may not be applied to a specific blocksize.

For example, when at least one of the width or the height of the currentblock is equal to or greater than a predetermined size, combined interintra prediction may not be applied. Here, the predetermined size may bea positive integer and may be, for example, 128. At this time,information indicating the combined inter intra prediction mode (e.g.,flag) may not be entropy-encoded/decoded.

When at least one of the width or the height of the current block isequal to or greater than the predetermined size (128) and a combinedinter intra prediction flag (ciip_flag) is not present in a bitstream,the combined inter intra prediction flag (ciip_flag) may be determinedas a second value (e.g., 1).

For example, when the area of the current block (or the number ofsamples included in the current block) is equal to or less than apredetermined value, combined inter intra prediction may not be applied.Here, the predetermined value may be a positive integer and may be, forexample, 64. At this time, information indicating a combined inter intraprediction mode (e.g., flag) may not be entropy-encoded/decoded.

When the area of the current block (or the number of samples included inthe current block) is less than the predetermined size (64) and acombined inter intra prediction flag (ciip_flag) is not present in abitstream, the combined inter intra prediction flag (ciip_flag) may bedetermined as a second value (e.g., 1).

The information indicating a combined inter intra prediction mode maymean a combined inter intra prediction flag.

For example, combined inter intra prediction may not be applied to achroma block having a size of 2×2. For example, combined inter intraprediction may not be applied to a luma block having a size of 4×4. Forexample, combined inter intra prediction may not be applied to a chromablock having a size of 4×4 or less. For example, combined inter intraprediction may not be applied to a luma block having a size of less than8×8.

For example, combined inter intra prediction may not be applied to achroma block having a size of 64×64. For example, combined inter intraprediction may not be applied to a luma block having a size of 128×128.For example, combined inter intra prediction may not be applied to aluma block having a size of greater than 64×64.

For example, combined inter intra prediction may not be applied to aluma block or a chroma block, the width of which is twice than theheight thereof.

For example, combined inter intra prediction may not be applied to aluma block or a chroma block, the height of which is twice than theweight thereof.

Intra prediction in combined inter intra prediction may be performed ina predefined intra prediction mode.

For example, intra prediction in combined inter intra prediction may useonly any one of a non-directional mode (Planar mode or DC mode).

Inter prediction in combined inter intra prediction may be performed ina predefined inter prediction mode.

For example, inter prediction in combined inter intra prediction may useonly at least one of uni-prediction or bi-prediction.

FIG. 8 is a flowchart illustrating an encoding/decoding method usingcombined inter intra prediction.

Referring to FIG. 8 , the combined inter intra prediction method mayinclude [1] generating an inter prediction block, [2] generating anintra prediction block and [3] combining the intra prediction block andthe inter prediction block.

Although [1] generating of an inter prediction block and [2] generatingof an intra prediction block are described as being performed in thisorder in FIG. 8 , the generating of the intra prediction block may beperformed before the generating of the inter prediction block.

In [3] combining of the intra prediction block and the inter predictionblock of FIG. 8 , a block obtained by combining the intra predictionblock and the inter prediction block may be referred to as a finalprediction block.

After the final prediction block is generated according to the combinedinter intra mode, at least one of processes such as transform/inversetransform, quantization/dequantization, entropy encoding/decoding,deblocking filtering, adaptive sample offset, adaptive in-loopfiltering, DMVR (Decoder-side Motion Vector Refinement), BDOF(Bi-Directional Optical Flow), PROF (Prediction Refinement with OpticalFlow), or BCW (Bi-prediction with CU-level weight) may be skipped. Here,skip of at least one of the processes may mean that at least one of theprocesses may not be performed with respect to the final predictionblock. In addition, skip of at least one of the processes may mean thatat least one of the processes may not be performed with respect to atleast one of prediction blocks.

In this specification, the combined inter intra mode may mean a mode inwhich combined inter picture intra picture prediction is performed. Inaddition, in this specification, the combined inter intra mode may meana mode in which combined inter intra prediction is performed. Inaddition, in this specification, the combined inter intra predictionmode may mean a combined inter intra mode.

DMVR may mean that a motion vector value is refined on the decoder side.For example, DMVR may mean that a corrected motion vector is derived bycorrecting a motion vector derived using a motion information predictionmethod such as a merge mode in order to improve accuracy of the motionvector.

DMVR may be performed in case of bidirectional prediction. In this case,bidirectional reference pictures are opposite to each other and may bereference pictures located at the same distance as the current picture.

Refinement of the motion vector value may be performed in units of N×Msubblocks. At this time, each of N and M may be a multiple of 2 in arange from 4 to 64. In addition, the N and M may be the same value ordifferent values.

Refinement of the motion vector value may be performed through one ormore reference picture lists.

For example, the prediction blocks and the motion vectors of a firstreference picture list and a second reference picture list may be used.

For example, only the prediction block and the motion block of the firstreference picture list may be used.

For example, only the prediction block and the motion block of thesecond reference picture list may be used.

At this time, the prediction block may be generated using interpolationblock.

For example, the prediction block may be generated using bilinearinterpolation filtering.

For example, the prediction block may be generated using DCTinterpolation filtering.

For example, the prediction block may be generated using bicubicfiltering.

At this time, the motion vector value may be refined using theprediction block of the reference picture list and blocks adjacent tothe block.

As the adjacent blocks, one or more of the blocks located in the topleft, left, bottom left, top, top right, right, bottom right and bottomdirections of the prediction block may be used.

The motion vector value may be refined through comparison between sumsof absolute differences (SADs) obtained by using the motion vectorvalues of the adjacent blocks.

At this time, the SADs may be adjusted for more accurate refinement ofthe motion vector.

For example, the SAD obtained by using the motion vector value of theprediction block may be reduced to ¼.

For example, the SAD obtained by using the motion vector value of theprediction block may be reduced to ½.

For example, the SAD obtained by using the motion vector value of theprediction block may be reduced to ⅛.

BDOF may mean that a prediction value is refined using bidirectionaloptical flow on the decoder side. For example, BODF may mean that acorrected prediction sample is derived by correcting a prediction samplegenerated by bidirectional prediction.

Refinement of the prediction value may be performed in units of N×Msubblocks. At this time, each of N and M may be a multiple of 2 in arange from 4 to 64. In addition, the N and M may be the same value ordifferent values.

Refinement of the prediction value may be performed through one or morereference picture lists.

For example, the prediction blocks of the first reference picture listand the second reference picture list and the optical flow accordingthereto may be obtained and used.

For example, the prediction block of the first reference picture listand the optical flow according thereto may be obtained and used.

For example, the prediction block of the second reference picture listand the optical flow according thereto may be obtained and used.

At this time, the prediction block may be generated using interpolationblock.

For example, the prediction block may be generated using bilinearinterpolation filtering.

For example, the prediction block may be generated using DCTinterpolation filtering.

For example, the prediction block may be generated using bicubicfiltering.

In addition, interpolation filtering in respective directions may besimultaneously or independently performed.

For example, interpolation filtering in a vertical direction may beperformed after interpolation filtering in a horizontal direction.

For example, interpolation filtering in a horizontal direction may beperformed after interpolation filtering in a vertical direction.

For example, interpolation filtering in a horizontal direction andinterpolation filtering in a vertical direction may be simultaneouslyperformed.

At this time, whether to perform the processes may be indicated througha flag value, and the flag value may be transmitted in a high-levelsyntax element such as a sequence parameter set, an adaptive parameterset, a picture parameter set, a tile header, a tile group header or aslice header.

The flag value indicating whether to perform the processes may becombined and transmitted.

For example, one flag may be transmitted by combining a flag fordecoder-side motion vector refinement and a flag for bidirectionaloptical flow.

For example, one flag may be transmitted by combining a flag forbidirectional optical flow and a flag for prediction refinement usingoptical flow.

For example, one flag may be transmitted by combining a flag fordecoder-side motion vector refinement, a flag for bidirectional opticalflow and a flag for prediction refinement using optical flow.

The combined inter intra prediction enabled flag ciip_enabled_flag mayindicate whether combined inter intra prediction is enabled. Thecombined inter intra prediction enabled flag ciip_enabled_flag may besignaled in a high-level syntax element such as a sequence parameterset, an adaptive parameter set, a picture parameter set, a pictureheader, a tile header, a tile group header or a slice header. Here, theadaptive parameter set may mean a parameter set referenced in severalpictures, several tile groups, several tiles, several slices, severalCTUs, etc. The combined inter intra prediction flag ciip_flag mayindicate whether to apply combined inter intra prediction. The combinedinter intra prediction flag ciip_flag may be signaled in units of atleast one of CTUs, CUs, PUs, TUs, CBs, PBs or TBs. When the combinedinter intra prediction flag ciip_flag has a first value (e.g., 0), thismay mean that combined inter intra prediction is not performed in unitsof at least one of CTUs, CUs, PUs, TUs, CBs, PBs or TBs. In addition,when the combined inter intra prediction flag ciip_flag indicates asecond value (e.g., 1), this may mean that combined inter intraprediction is performed in units of at least one of CTUs, CUs, PUs, TUs,CBs, PBs or TBs.

When the combined inter intra prediction enabled flag ciip_enabled_flagindicates a first value (e.g., 0), the combined inter intra predictionflag ciip_flag may not be signaled via a bitstream. In addition, whenthe combined inter intra prediction enabled flag ciip_enabled_flagindicates a second value (e.g., 1), the combined inter intra predictionflag ciip_flag may be signaled through a bitstream.

When the combined inter intra prediction enabled flag ciip_enabled_flaghas a second value (e.g., 1) and the combined inter intra predictionflag ciip_flag is not present in a bitstream, the combined inter intraprediction flag ciip_flag may be determined as a second value (e.g., 1).

That is, the combined inter intra prediction enabled flagciip_enabled_flag indicates a first value, this may indicate that thecombined inter intra prediction mode is not used in the sequence,picture, tile or slice unit, to which the flag is applied. In addition,when the combined inter intra prediction enabled flag ciip_enabled_flagindicates a second value, this may indicate that the combined interintra prediction mode is used in the sequence, picture, tile or sliceunit, to which the flag is applied. For example, when the combined interintra prediction flag ciip_flag has a first value, [2] and [3] of FIG. 8may not be performed, and the block generated through inter predictiongenerated in [1] of FIG. 8 may be used as a final prediction block. Inaddition, when the combined inter intra prediction flag ciip_flag has asecond value, the process of FIG. 8 may be performed. At this time, thefirst value may be 0 and the second value may be 1. That is, when thecombined inter intra prediction flag ciip_flag has a first value (0),this may mean false as a Boolean value. In addition, when the combinedinter intra prediction flag ciip_flag has a second value (1), this maymean true as a Boolean value.

At least one of the processes such as transform/inverse transform,quantization/dequantization, entropy encoding/decoding, deblockingfiltering, adaptive sample offset, adaptive in-loop filtering, DMVR(Decoder-side Motion Vector Refinement), BDOF (Bi-Directional OpticalFlow), PROF (Prediction Refinement with Optical Flow), or BCW(Bi-prediction with CU-level weight) may not be performed according tothe value of the combined inter intra prediction flag ciip_flag.

For example, when combined inter intra prediction is not applied, thecombined inter intra prediction flag ciip_flag may have a first value(0). At this time, when the combined inter intra prediction flagciip_flag has a first value (0), the DMVR (Decoder-side Motion VectorRefinement) process may be performed. That is, when the combined interintra prediction flag ciip_flag has a first value (0), a flag indicatingwhether to perform the DMVR process may be set to a second value (1) andthus the DMVR process may be performed.

In contrast, when combined inter intra prediction is applied, thecombined inter intra prediction flag ciip_flag may have a second value(1). At this time, when the combined inter intra prediction flagciip_flag has a second value (1), the DMVR process may not be performed.That is, when the combined inter intra prediction flag ciip_flag has asecond value (1), a flag indicating whether to perform the DMVR processmay be set to a first value (0) and thus the DMVR process may not beperformed.

For example, when combined inter intra prediction is not applied, thecombined inter intra prediction flag ciip_flag may have a first value(0). At this time, when the combined inter intra prediction flagciip_flag has a first value (0), the BDOF (Bi-Directional Optical Flow)or PROF (Prediction Refinement with Optical Flow) process may beperformed. That is, when the combined inter intra prediction flagciip_flag has a first value (0), a flag indicating whether to performthe BDOF or PROF process may be set to a second value (1) and thus theBDOF or PROF process may be performed.

In contrast, when combined inter intra prediction is applied, thecombined inter intra prediction flag ciip_flag may have a second value(1). At this time, when the combined inter intra prediction flagciip_flag has a second value (1), the BDOF (Bi-Directional Optical Flow)or PROF (Prediction Refinement with Optical Flow) process may not beperformed. That is, when the combined inter intra prediction flagciip_flag has a second value (1), a flag indicating whether to performthe BDOF or PROF process may be set to a first value (0) and thus theBDOF or PROF process may not be performed.

For example, when combined inter intra prediction is not applied, thecombined inter intra prediction flag ciip_flag may have a first value(0). At this time, when the combined inter intra prediction flagciip_flag has a first value (0), the BCW (Bi-prediction with CU-levelweight) process may be performed. That is, when the combined inter intraprediction flag ciip_flag has a first value (0), a flag indicatingwhether to perform the BCW process may be set to a second value (1) andthus the BCW process may be performed. Here, when the weight index valueof bidirectional weight prediction is not a first value (e.g., 0) andthe combined inter intra prediction flag ciip_flag has a first value(0), the bidirectional weight prediction may be performed. At this time,combined inter intra prediction may not be performed but thebidirectional weight prediction may be performed. That is, combinedinter intra prediction and bidirectional weight prediction may beperformed mutually exclusively.

In contrast, when combined inter intra prediction is applied, thecombined inter intra prediction flag ciip_flag may have a second value(1). At this time, when the combined inter intra prediction flagciip_flag has a second value (1), the BCW process may not be performed.That is, when the combined inter intra prediction flag ciip_flag has asecond value (1), a flag indicating whether to perform BCW process maybe set to a first value (0) and thus the BCW process may not beperformed. Here, when the weight index value of bidirectional weightprediction is a first value (e.g., 0) or the combined inter intraprediction flag ciip_flag has a second value (1), combined inter intraprediction may be performed. At this time, bidirectional weightprediction may not be performed but combined inter intra prediction maybe performed. That is, combined inter intra prediction and bidirectionalweight prediction may be performed mutually exclusively.

When the weight index of the bidirectional weight prediction has a firstvalue, this may mean that the same weight is used for two predictionblocks. In addition, when the weight index of the bidirectional weightprediction does not have a first value, this may mean that differentweights are used for two prediction blocks.

[1] Generation of the Inter Prediction Block

Through inter prediction, the prediction block of the current block maybe generated based on information included in at least one of a previouspicture or a subsequent picture of the current picture. At this time,the encoder/decoder may generate the prediction block of the currentblock through motion information necessary for inter prediction. Here,the motion information may mean a motion vector, a reference pictureindex, etc. The prediction block of the current block may be generatedbased on the reference picture indicated by the reference picture indexand the motion vector.

When the prediction block is generated through combined inter intraprediction, at least one of the inter prediction modes may be performed.At this time, the inter prediction modes may include a skip mode, aregular merge mode, an AMVP mode, an affine mode, a sub-block basedmerge mode, a sub-block based temporal merge mode, a BDOF(Bi-directional Optical Flow) mode, a triangular partition mode, an MMVD(Merge with Motion Vector Difference) mode and a DMVR (Decoder-sideMotion vector refinement) mode.

For example, when the inter prediction mode is a merge mode, an interprediction block may be generated using information on the merge mode.At this time, in the intra prediction mode, an intra prediction blockmay be generated through a planar mode which is a non-directionalprediction mode. In addition, a final prediction block may be generatedby combining the intra prediction block and the inter prediction block.At this time, the information on the merge mode may mean a mergecandidate list, a motion vector, a reference picture index, etc.

In the embodiment, when the information on the merge mode istransmitted, intra prediction may be performed and information on theintra prediction mode may be entropy-encoded/decoded. At this time, theinformation on intra prediction may mean an intra prediction flag, anintra prediction candidate mode list flag, an intra prediction candidatemode index, etc. and at least one of the information may beentropy-encoded/decoded.

In addition, when combined inter intra prediction is performed,information on intra prediction may not be entropy-encoded/decoded andthe Planar mode may be used as the intra prediction mode.

For example, when the inter prediction mode is an AMVP mode, a currentblock may be generated using information on the AMVP mode. At this time,in the intra prediction mode, a block may be generated through a Planarmode which is a non-directional prediction mode. A final prediction modemay be generated by combining the intra prediction block and the interprediction block using the generated blocks. At this time, theinformation on the AMVP mode may mean a motion vector difference value,a reference picture index, a motion vector prediction value candidatelist, etc.

For example, when the inter prediction mode is an AMVP mode, a currentblock may be generated using information on the AMVP mode. At this time,the information on the AMVP mode may mean a motion vector differencevalue, a reference picture index, a motion vector prediction valuecandidate list, etc.

In the embodiment, when the information on the AMVP mode is transmitted,intra prediction may be performed and information on the intraprediction mode may be entropy-encoded/decoded. At this time, theinformation on the intra prediction may mean an intra prediction flag,an intra prediction candidate mode list flag, an intra predictioncandidate mode index, etc. and at least one of the information may beentropy-encoded/decoded.

For example, when the inter prediction mode is not a sub-block basedmerge mode, a regular merge mode, a skip mode and an MMVD mode, thecombined inter intra prediction mode may be performed. That is, when theinter prediction mode is at least one of a sub-block based merge mode, aregular merge mode and an MMVD mode, [2] and [3] of FIG. 8 may not beperformed.

When the inter prediction mode is not at least one of a sub-block basedmerge mode, a regular merge mode, a skip mode and an MMVD mode and thecombined inter intra prediction flag ciip_flag is not present in abitstream, the combined inter intra prediction flag ciip_flag may bedetermined as a second value (e.g., 1).

The MMVD mode may mean a type of merge mode in which a motion vectordifference value is additionally used.

[2] Generation of the Intra Prediction Block

In the intra prediction process, a prediction block may be generatedusing a predefined intra prediction mode or the intra prediction mode ofthe current block. At this time, the predefined intra prediction modemay mean one or more of a non-directional mode which is the intraprediction mode or a directional mode.

For example, one predefined intra prediction mode may be used for theintra prediction process. At this time, as the intra prediction mode, aPlanar mode which is a non-directional mode may be used.

For example, two predefined intra prediction modes may be used for theintra prediction process. At this time, as the intra prediction mode,one non-directional mode and one directional mode may be used.Alternatively, two non-directional modes may be used or two directionalmodes may be used.

For example, four predefined intra prediction modes may be used for theintra prediction process. At this time, as the intra prediction mode,one non-directional mode and three directional modes may be used.Alternatively, two non-directional modes and two directional modes maybe used, or four directional modes may be used.

Since a probability that the intra prediction mode of the current blockis equal to the intra prediction modes of adjacent neighbor blocks whichhave been already encoded/decoded is high, the intra prediction mode ofthe current block may be derived using the intra prediction modes of theneighbor blocks. At this time, the neighbor blocks adjacent to thecurrent block may mean at least one of top, bottom, left, right, topleft, top right or bottom left blocks with a location difference of Npixels from the boundary of the current block. N may be a positiveinteger value including 0.

In the intra prediction mode process, a prediction block may begenerated using the reference pixel of a block adjacent to the currentblock. At this time, the neighbor block adjacent to the current blockmay mean at least one of top, bottom, left, right, top left, top rightor bottom left block with a location difference of N pixels from theboundary of the current block. N may be a positive integer valueincluding 0.

In order to perform the intra prediction mode process, smooth filteringmay be performed with respect to the reference pixel of the adjacentblock according to a specific condition. At this time, smooth filteringmay be represented through Equation 1.

filteredref[x]=(first value*ref[x−1]+second value*ref[x]+firstvalue*ref[x+1]+N)>>M  Equation 1

where, filteredref denotes a reference pixel value, to which smoothfiltering is applied, and ref denotes a reference pixel value beforesmooth filter is applied. X denotes the location of a currentlyreferenced pixel, and x−1 and x+1 may indicate left and right pixelvalues or upper and lower pixel values.

Here, N and M may be a positive integer and M may be 3 or N and M may be2.

For example, when the sum of the first value and the second value is 16,M may be 4.

In another example, when the sum of the first value and the second valueis 8, M may be 3.

In another example, when the sum of the first value and the second valueis 4, M may be 2.

In another example, when the sum of the first value and the second valueis 2, M may be 1.

For example, when M is 2, N may be 2.

For example, when M is 3, N may be 4.

Here, the specific condition may be limited through at least one of thesize of the block, the width of the block, the height of the block orciip_flag.

For example, when the width of the block*the height of the block, whichindicates the size of the block, is greater than or equal to a thresholdTHR, smooth filtering may be performed. The threshold THR may be anarbitrary positive value including 0.

In another example, when the width of the block is greater than or equalto the threshold THR, smooth filtering may be performed.

In another example, when the height of the block is greater than orequal to the threshold THR, smooth filtering may be performed.

In another example, when ciip_flag has a third value, smooth filteringmay be performed.

In another example, when ciip_flag has a fourth value and the width ofthe block is greater than or equal to the threshold THR, smoothfiltering may be performed. At this time, the fourth value may mean 0.

In another example, when ciip_flag has a fourth value and the height ofthe block is greater than or equal to the threshold THR, smoothfiltering may be performed. At this time, the fourth value may mean 0.

In another example, when ciip_flag has a fourth value and the width ofthe block*the height of the block, which indicates the size of theblock, is greater than or equal to a threshold THR, smooth filtering maybe performed.

Here, the third value may mean 1 and the fourth value may mean 0.

Here, the threshold THR may be an arbitrary positive value including 0.

MPM (Most Probable Mode) candidate modes which are candidate modes usedto the intra prediction mode of the current block may be added to an MPMcandidate mode list. At this time, when the prediction block isgenerated using a Planar mode or a DC mode which is a specificprediction mode, the MPM candidate mode list may not be used.

The MPM candidate mode may mean an intra prediction candidate mode. Theencoder/decoder may derive an MPM candidate mode from the predictionmodes of the neighbor blocks adjacent to the current block. Among theprediction modes of the neighbor blocks, a first prediction mode may berepresented by candIntraPredModeA and a second prediction mode may berepresented by candIntraPredModeB.

For example, when the first prediction mode is the prediction mode of aleft neighbor block and the second prediction mode is the predictionmode of a top neighbor block, candIntraPredModeA may mean the predictionmode of the left neighbor block or the top neighbor block andcandIntraPredModeB may mean the prediction mode of the left neighborblock or the top neighbor block.

For example, when the first prediction mode is the prediction mode of atop right neighbor block and the second prediction mode is theprediction mode of a bottom left neighbor block, candIntraPredModeA maymean the prediction mode of the top right neighbor block or the bottomleft neighbor block, and candIntraPredModeB may mean the prediction modeof the top right neighbor block or the bottom left neighbor block.

For example, when ciip_flag has a first value, a block may be generatedthrough a DC mode, which is a non-directional mode, in the intraprediction mode, and the MPM candidate mode list may not be used.

For example, when ciip_flag has a first value, a block may be generatedthrough a Planar mode, which is a non-directional mode, in the intraprediction mode, and the MPM candidate mode list may not be used.

For example, when ciip_flag has a first value, a block may be generatedthrough a specific directional mode in the intra prediction mode, andthe MPM candidate mode list may not be used.

Assignment of the prediction candidate mode to the MPM candidate modelist and prediction mode determination may vary according to theprediction mode values of the neighbor blocks. The number of candidatemodes in the MPM candidate mode list may be N. At this time, N may be anarbitrary positive integer including 0.

For example, an N-th prediction mode value may be used without change toassign the prediction candidate mode to the MPM candidate mode list ormay be changed to another value to be used to assign the predictioncandidate mode to the MPM candidate mode list.

For example, when the N-th prediction mode is above a diagonal mode, avertical mode may be assigned to the N-th prediction mode. At this time,the mode value of the diagonal mode may be 34, and the mode value of thevertical mode may be

For example, when the N-th prediction mode is above ahorizontal-diagonal mode and is at a diagonal mode or below a diagonalmode, a horizontal mode may be assigned to the N-th prediction mode. Atthis time, the mode value of the horizontal-diagonal mode may be 2, themode value of the diagonal mode may be 34, and the mode value of thehorizontal value may be 18.

For example, when the N-th prediction mode is a non-directional mode,the corresponding prediction mode (the N-th prediction mode) may beassigned to the N-th prediction mode.

In the above embodiment, N may mean 1 or 2.

At this time, the first value may mean 1.

FIG. 9 is a flowchart illustrating a method of assigning a predictionmode to an MPM candidate mode list.

In the MPM candidate mode assignment {circle around (1)} of FIG. 9 ,when the first prediction mode and the second prediction mode are thesame and the corresponding prediction mode (the first prediction mode)is a non-directional mode, the non-directional mode and the Verticalmode may be assigned to the MPM candidate mode list.

For example, when the first prediction mode and the second predictionmode are the same and the corresponding prediction mode (the firstprediction mode) is a Planar mode or a DC mode, the Planar mode, the DCmode and the Vertical mode may be assigned to the MPM candidate modelist. At this time, the mode value of the Vertical mode may be 50.

In the MPM candidate mode assignment {circle around (2)} of FIG. 9 ,when the first prediction mode and the second prediction mode are thesame and the corresponding prediction mode (the first prediction mode)is a directional mode, the corresponding prediction mode (the firstprediction mode) and the non-directional mode may be assigned to the MPMcandidate mode list.

For example, when the first prediction mode and the second predictionmode are the same and the corresponding prediction mode (the firstprediction mode) is a directional mode, the corresponding predictionmode (the first prediction mode), the Planar mode, and the DC mode maybe assigned to the MPM candidate mode list.

In the MPM candidate mode assignment {circle around (3)} of FIG. 9 ,when the first prediction mode and the second prediction mode are notthe same and both the two prediction modes are not a Planar mode, thefirst prediction mode, the second prediction mode and the Planar modemay be assigned to the MPM candidate mode list.

For example, when the first prediction mode and the second predictionmode are not the same and both the two prediction modes are directionalmodes or only one of the two prediction modes is a DC mode and the otherprediction mode is a directional mode, the first prediction mode, thesecond prediction mode, and the Planar mode may be assigned to the MPMcandidate mode list.

In the MPM candidate mode assignment {circle around (4)} of FIG. 9 ,when the first prediction mode and the second prediction mode are notthe same and both the two prediction modes are not DC modes, the firstprediction mode, the second prediction mode and the DC mode may beassigned to the MPM candidate mode list.

For example, when the first prediction mode and the second predictionmode are not the same and only one of the two prediction modes is aPlanar mode and the other prediction mode is a directional mode, thefirst prediction mode, the second prediction mode, and the DC mode maybe assigned to the MPM candidate mode list.

In the MPM candidate mode assignment {circle around (5)} of FIG. 9 ,when the first prediction mode and the second prediction mode are notthe same and both the two prediction modes are non-directional modes,the first prediction mode, the second prediction mode and the Verticalmode may be assigned to the MPM candidate mode list.

For example, when the first prediction mode and the second predictionmode are not the same and the two prediction modes are respectively aPlanar mode and a DC mode, the first prediction mode, the secondprediction mode, and the Vertical mode may be assigned to the MPMcandidate mode list. At this time, the mode value of the Vertical modemay be 50.

FIG. 10 is a flowchart illustrating a method of assigning a predictionmode to an MPM candidate mode list.

In the MPM candidate mode assignment {circle around (1)} of FIG. 10 ,when the first prediction mode and the second prediction mode are thesame and the corresponding prediction mode (the first prediction mode)is a non-directional mode, the corresponding prediction mode (the firstprediction mode) may be assigned to the MPM candidate mode list. Whenthe corresponding prediction mode (the first prediction mode) is aPlanar mode, the DC mode may be assigned to the MPM candidate mode list,and, when the corresponding prediction mode (the first prediction mode)is a DC mode, the Planar mode may be assigned to the MPM candidate modelist. The Vertical mode, the Horizontal mode, (Vertical−4) mode, and(Vertical+4) mode may be assigned to the remaining list. The mode valueof the Vertical mode may be 50, the mode value of the Horizontal modemay be 18, the mode value of the (Vertical−4) mode may be 46, and themode value of (Vertical+4) mode may be 54. Under the above condition, atleast one of the modes may be assigned to the MPM candidate mode list.

In the MPM candidate mode assignment {circle around (2)} of FIG. 10 ,when the first prediction mode and the second prediction mode are thesame and the corresponding prediction mode (the first prediction mode)is a directional mode, the corresponding prediction mode (the firstprediction mode) and the Planar mode and the DC mode, both of which arethe non-directional modes, may be assigned to the MPM candidate modelist, and the prediction modes adjacent to the corresponding predictionmode (the first prediction mode) may be assigned to the list. In thisspecification, the adjacent prediction mode may mean a prediction modevalue which is a result obtained by adding or subtracting an N value toor from a specific prediction mode value. Herein, N may be a positiveinteger. In particular, when N is less than a specific value M, this maybe referred to as a prediction mode adjacent to a specific predictionmode.

For example, when the first prediction mode and the second predictionmode are the same, the first prediction mode, the Planar mode, the DCmode, (the first prediction mode−1) mode, (the first prediction mode+1)mode, (the first prediction mode−2) mode may be assigned to the MPMlist. At this time, when the mode adjacent to the first prediction modeor the second prediction mode is a non-directional mode, a directionalmode located in an opposite direction may be assigned to the list.

In the MPM candidate mode assignment {circle around (3)} of FIG. 10 ,when both the first prediction mode and the second prediction mode aredirectional modes, the first prediction mode and the second predictionmode may be assigned to the MPM candidate mode list, the Planar mode andthe DC mode, which are the non-directional modes, may be assigned to theMPM candidate mode list. In addition, a difference value (maxAB−minAB)between two prediction modes may be obtained, and, when a differencebetween two values is 2 or more and 62 or less, prediction modesadjacent to the maxAB mode may be assigned to the remaining MPMcandidate mode list.

In this specification, minAB may mean a mode having the smaller valuebetween the first prediction mode and the second prediction mode, andmaxAB may mean a mode having the larger value between the firstprediction mode and the second prediction mode.

For example, when the first prediction mode is a directional mode andthe second prediction mode is a directional mode, the first predictionmode and the second prediction mode may be assigned to the MPM candidatemode list. At this time, the mode having the larger value between twoprediction modes may be set as maxAB, and the mode having the smallervalue may be set as minAB. When a difference between the maxAB modevalue and the minAB mode value is 2 or more and 62 or less, the Planarmode, the DC mode, the (maxAB−1) mode, and the (maxAB+1) mode may beassigned to the remaining list.

When a difference maxAB−minAB between two prediction modes is 1 or lessand 63 or more, as in the MPM candidate mode assignment {circle around(4)}, a prediction mode adjacent to the maxAB and a prediction modeadjacent to the minAB mode may be assigned to the remaining MPMcandidate mode list.

For example, when the first prediction mode is a directional mode andthe second prediction mode is a directional mode, the first predictionmode and the second prediction mode may be assigned to the MPM candidatemode list. At this time, the mode having the larger value between twoprediction modes may be set as maxAB, and the mode having the smallervalue may be set as minAB. When a difference between the maxAB modevalue and the minAB mode value is 1 or less and 63 or more, the Planarmode, the DC mode, the (maxAB−2) mode, and the (maxAB+2) mode may beassigned to the remaining list.

In the MPM candidate mode assignment {circle around (5)} of FIG. 10 ,when the first prediction mode and the second prediction mode are notthe same, only one of two prediction modes is a non-directional mode andthe other prediction mode is a directional mode, the first predictionmode and the second prediction mode may be assigned to the MPM candidatemode list. When the non-directional mode assigned to the list is aPlanar mode, the DC mode may be assigned and, when the prediction modeis a DC mode, the Planar mode may be assigned to the list. Theprediction mode adjacent to the directional mode may be assigned to theremaining candidate mode list.

For example, when the first prediction mode is a Planar mode and thesecond prediction mode is a directional mode, the Planar mode and thesecond prediction mode may be assigned to the MPM candidate mode list.At this time, the mode having the larger value between two predictionmodes may be set as maxAB, and the mode having the smaller value may beset as minAB. The DC mode, the (maxAB−1) mode, the (maxAB+1) mode, andthe (maxAB−2) mode may be assigned to the remaining list. At this time,when the mode adjacent to the second prediction mode is anon-directional mode, a directional mode located in an oppositedirection may be assigned to the list.

In the MPM candidate mode assignment {circle around (1)} of FIG. 10 ,when the first prediction mode and the second prediction mode are notthe same and the first prediction mode and the second prediction modeare non-directional modes, the first prediction mode and the secondprediction mode may be assigned to the MPM candidate mode list. TheVertical mode, the Horizontal mode, the (Vertical−4) mode, and the(Vertical+4) mode may be assigned to the remaining mode. The mode valueof the Vertical mode may be 50, the mode value of the Horizontal modemay be 18, the mode value of the (Vertical−4) mode may be 46, and themode value of the (Vertical+4) mode may be 54. Under the abovecondition, at least one of the modes may be assigned to the MPMcandidate mode list.

For example, when the first prediction mode is a Planar mode and thesecond prediction mode is a DC mode, the Planar mode and the DC mode maybe assigned to the MPM candidate mode list. The Vertical mode, theHorizontal mode, the (Vertical−4) mode and the (Vertical+4) mode may beassigned to the remaining list. The mode value of the Vertical mode maybe 50, the mode value of the Horizontal mode may be 18, the mode valueof the (Vertical−4) mode may be 46, and the mode value of the(Vertical+4) mode may be 54.

Among the MPM candidate mode assignment methods, in a method ofdetermining which of the first prediction mode and the second predictionmode is a directional mode or a non-directional mode,

when the non-directional mode is assigned to relatively low numbers, byobtaining the larger value maxAB between the first prediction mode andthe second prediction mode, it is possible to derive the directionalmode and determine the remaining mode as the non-directional mode.

Alternatively, when the non-directional mode is assigned to relativelyhigh numbers, by obtaining the smaller value minAB between the firstprediction mode and the second prediction mode, it is possible to derivethe directional mode and determine the remaining modes as thenon-directional mode.

For example, in the MPM candidate mode assignment {circle around (5)},by obtaining the larger value maxAB between the two modes in order todetermine which of the two prediction modes is a directional mode, it ispossible to determine the directional mode.

The MPM candidate mode list may be updated according to information onthe current block. At this time, the information on the current blockmay mean the width of the current block, the height of the currentblock, the ratio of the width to the height of the current block, thearea of the current block, etc.

For example, when the height of the current block is equal to or twicethan the width of the current block and the Vertical mode is present inthe MPM candidate mode list, another prediction candidate mode may beassigned to the MPM candidate mode list instead of the Vertical mode. Atthis time, assigning another prediction candidate mode instead of theVertical mode may mean that another prediction candidate mode isassigned to an index location, in which the Vertical mode is present, inthe MPM candidate mode list.

In the embodiment, when the Planar mode is not present in the MPMcandidate mode list, the Planar mode may be assigned to the MPMcandidate mode list instead of the Vertical mode.

In the embodiment, when the DC mode is not present in the MPM candidatemode list, the DC mode may be assigned to the MPM candidate mode listinstead of the Vertical mode.

In the embodiment, when the Vertical mode is not present in the MPMcandidate mode list, the Vertical mode may be assigned to the MPMcandidate mode list instead of the Horizonal mode.

In the embodiment, when the Horizontal mode is not present in the MPMcandidate mode list, the Horizontal mode may be assigned to the MPMcandidate mode list instead of the Vertical mode.

In the embodiment, the mode value of the Vertical mode may be 50, andthe mode value of the Horizontal mode may be 18.

For example, when the width of the current block is equal to or twicethan the height of the current block and the Horizontal mode is presentin the MPM candidate mode list, another prediction candidate mode may beassigned to the MPM candidate mode list instead of the Horizontal mode.At this time, assigning another prediction candidate mode instead of theHorizontal mode may mean that another prediction candidate mode isassigned to an index location, in which the Horizontal mode is present,in the MPM candidate mode list.

In the embodiment, when the Planar mode is not present in the MPMcandidate mode list, the Planar mode may be assigned to the MPMcandidate mode list instead of the Horizontal mode.

In the embodiment, when the DC mode is not present in the MPM candidatemode list, the DC mode may be assigned to the MPM candidate mode listinstead of the Horizontal mode.

In the embodiment, when the Vertical mode is not present in the MPMcandidate mode list, the Vertical mode may be assigned to the MPMcandidate mode list instead of the Horizontal mode.

In the embodiment, when the Horizontal mode is not present in the MPMcandidate mode list, the Horizontal mode may be assigned to the MPMcandidate mode list instead of the Vertical mode.

In the embodiment, the mode value of the Vertical mode may be 50, andthe mode value of the Horizontal mode may be 18.

The encoder/decoder may generate a prediction block, by assigning allprediction modes to the MPM candidate mode list and then determining theintra prediction mode.

At this time, an MPM flag indicating whether the same mode as theprediction mode of the current block is present in the MPM candidatemode list may be entropy-encoded/decoded, and the flag may berepresented by intra_luma_mpm_flag. When intra_luma_mpm_flag has a firstvalue, this may mean that the same mode as the prediction mode of theblock to be encoded/decoded is not present in the MPM candidate modelist. When intra_luma_mpm_flag has a second value, this may mean thatthe same mode as the prediction mode of the block to be encoded/decodedis present in the MPM candidate mode list.

When intra_luma_mpm_flag is present and the flag has a first value, theintra prediction mode may be determined using the prediction candidatemodes assigned in the MPM candidate mode list.

For example, when the Planar mode is not present in the MPM candidatemode list, the Planar mode may be determined as the intra predictionmode.

For example, when the DC mode is not present in the MPM candidate modelist, the DC mode may be determined as the intra prediction mode.

For example, when the Vertical mode is not present in the MPM candidatemode list, the Vertical mode may be determined as the intra predictionmode. At this time, the mode value of the Vertical mode may be 50.

For example, when the Horizontal mode is not present in the MPMcandidate mode list, the Horizontal mode may be determined as the intraprediction mode. At this time, the mode value of the Horizontal mode maybe 18.

When intra_luma_mpm_flag is present and the flag has a second value, theMPM index may be additionally entropy-encoded/decoded. The MPM indexindicates to which of the candidate modes in the MPM candidate mode listthe prediction mode of the block to be encoded/decoded is equal, and maybe represented by intra_luma_mpm_idx. The encoder/decoder may determine,as the intra prediction mode, a prediction candidate mode located at thecorresponding index intra_luma_mpm_idx in the MPM candidate mode list.

In the embodiment, the first value may be 0 and the second value may be1.

[3] Combination of the Intra Prediction Block and the Inter PredictionBlock

A final prediction block may be generated by giving a weight to aprediction block (or a prediction sample) generated by each method(inter prediction and intra prediction) in order to combine the intraprediction block and the inter prediction block. Here, a predictionblock sample generated through intra prediction may be represented bypredSamplesIntra and a prediction block sample generated through interprediction may be represented by predSamplesInter.

At this time, the weight may vary according to current blockinformation, neighbor block information, a quantization parameter (QP),etc., and the current/neighbor block information may mean the width ofthe current/neighbor block, the height of the current/neighbor block,the size of the current/neighbor block, the depth of thecurrent/neighbor block, the form (square/non-square) of thecurrent/neighbor block, the ratio of the width to the height of thecurrent/neighbor block, the location of the current/neighbor blocksample, the prediction mode of the current/neighbor block, the intraprediction mode of the current/neighbor block, the intra prediction modedirectionality of the current/neighbor block, the inter prediction modeof the current/neighbor block, the ratio of the inter prediction blockto the current/neighbor block, the ratio of the intra prediction blockto the current/neighbor block, the number of inter prediction blocks ofthe current/neighbor block, the number of intra prediction blocks of thecurrent/neighbor block, the number of intra prediction blocks having anon-directional prediction mode of the current/neighbor block, thenumber of intra prediction blocks having a directional prediction modeof the current/neighbor block, the weight of the neighbor block, etc. Atleast one of them may be used to give a weight. Here, as the block sizedecreases, the depth may increase.

The weight used in combined inter intra prediction may be determinedbased on the prediction mode of the neighbor block. Specifically, theweight used in combined inter intra prediction may be determined basedon whether at least one neighbor block is an intra prediction mode.Herein, the neighbor block may include a left neighbor block and a topneighbor block. At this time, the weight may mean a weight applied to ablock sample generated through intra prediction.

For example, when both the left neighbor block and the top neighborblock are in the intra prediction mode, the weight used in the combinedinter intra prediction may be set to a first value. Here, the firstvalue may be 3. When the weight used in the combined inter intraprediction is set to a first value, the weight for intra prediction inthe combined inter intra prediction may be set to a first value or ¾ andthe weight for inter prediction may be set to a third value or ¼.

In addition, when any one of the left neighbor block and the topneighbor block is in an intra prediction mode, the weight used incombined inter intra prediction may be set to a second value. Here, thesecond value may be 2. When the weight used in combined inter intraprediction is set to a second value, the weight for intra prediction inthe combined inter intra prediction may be set to a second value or 2/4and the weight for inter prediction may be set to a second value or 2/4.In addition, when both the left neighbor block and the top neighborblock are not in an intra prediction mode, the weight used in combinedinter intra prediction may be set to a third value. Here, the thirdvalue may be 1. When the weight used in the combined inter intraprediction is set to a third value, the weight for intra prediction inthe combined inter intra prediction may be set to a third value or ¼ andthe weight for inter prediction may be set to a first value or ¾.

In addition, the weight may be determined based on at least one of thecoding parameters of the current block.

Here, the weight applied to the intra prediction block may be determinedbased on at least one of the coding parameters related to the intraprediction of the current block.

In addition, the weight applied to the inter prediction block may bedetermined based on at least one of the coding parameters related to theinter prediction of the current block.

Among weights, a first weight may mean a weight for a block generatedthrough intra prediction and a second weight may mean a weight for ablock generated through inter prediction. Here, at least one of thefirst weight and the second weight may be a positive integer. At thistime, the same weight, that is, the first weight, is applicable to allor some of intra prediction blocks and the same weight, that is, thesecond weight, is applicable to all or some of the inter predictionblocks.

In this specification, although the first weight and the second weightare represented by numerators excluding the denominator for convenience,the present invention is not limited thereto and the first weight may be(the first weight/(the first weight+the second weight) and the secondweight may be (the second weight/(the first weight+the second weight).

For example, when both the left neighbor block and the top neighborblock are in the intra prediction mode, the first weight may be set to 3and the second weight may be set to 1.

In addition, when any one of the left neighbor block and the topneighbor block is in the intra prediction mode, the first weight may beset to 2 and the second weight may be set to 2.

In addition, when both the left neighbor block and the top neighborblock are not in the intra prediction mode, the first weight may be setto 1 and the second weight may be set to 3.

For example, when the intra prediction mode of the current block is aPlanar mode or a DC mode or when the width or height of the currentblock is less than 4, the first weight may be 4 and the second weightmay be 4.

For example, when the intra prediction mode of the current block is aHorizontal mode and the width and height of the current block is greaterthan 4, the first weight may be set through Table 1. The second weightmay be set to (8−the first weight). At this time, nPos may man the xcoordinate value of the current block and nSize may mean the width ofthe current block. The mode value of the Horizontal mode may be 18.

For example, when the intra prediction mode of the current block is aVertical mode and the width and height of the current block is greaterthan 4, the first weight may be set through Table 1. The second weightmay be set to (8−the first weight). At this time, nPos may mean the ycoordinate value of the current block and nSize may mean the height ofthe current block. The mode value of the Vertical mode may be 50.

TABLE 1 $0 \leq {nPos} < \frac{nSize}{4}$$\frac{nSize}{4} \leq {nPos} < \frac{nSize}{2}$$\frac{nSize}{2} \leq {nPos} < \frac{3 \times {nSize}}{4}$$\frac{3 \times {nSize}}{4} \leq {nPos} < {nSize}$ 6 5 3 2

For example, when the intra prediction mode of the current block islocated below the diagonal mode and the width and height of the currentblock is greater than 4, the first weight may be set through Table 2.The second weight may be set to (8−the first weight). At this time, nPosmay man the x coordinate value of the current block and nSize may meanthe width of the current block. The mode value of the diagonal mode maybe 34, and the mode located below the diagonal mode may mean a modehaving a value less than 34.

For example, when the intra prediction mode of the current block is at adiagonal mode or is located above the diagonal mode and the width andheight of the current block is greater than 4, the first weight may beset through Table 2. The second weight may be set to (8−the firstweight). At this time, nPos may man the y coordinate value of thecurrent block and nSize may mean the height of the current block. Themode value of the diagonal mode may be 34, and the mode located abovethe diagonal mode may mean a mode having a value greater than 34.

For example, when the intra prediction mode of the current block islocated below the diagonal mode and the width and height of the currentblock is greater than 4, the first weight may be set through Table 3.The second weight may be set to (8−the first weight). At this time, nPosmay man the x coordinate value of the current block and nSize may meanthe width of the current block. The mode value of the diagonal mode maybe 34, and the mode located below the diagonal mode may mean a modehaving a value less than 34.

For example, when the intra prediction mode of the current block is at adiagonal mode or is located above the diagonal mode and the width andheight of the current block is greater than 4, the first weight may beset through Table 3. The second weight may be set to (8−the firstweight). At this time, nPos may man the y coordinate value of thecurrent block and nSize may mean the height of the current block. Themode value of the diagonal mode may be 34, and the mode located abovethe diagonal mode may mean a mode having a value greater than 34.

For example, when the intra prediction mode of the current block is adirectional mode excluding the Horizontal mode and the Vertical mode andthe width and height of the current block is greater than 4, the firstweight may be set to 4 and the second weight may be set to 4. The modevalue of the Horizontal mode may be 18, and the mode value of theVertical mode may be 50.

TABLE 2 $0 \leq {nPos} < \frac{nSize}{2}$$\frac{nSize}{2} \leq {nPos} < {nSize}$ 6 2

TABLE 3 $0 \leq {nPos} < \frac{nSize}{2}$$\frac{nSize}{2} \leq {nPos} < {nSize}$ 5 3

For example, the first weight may be 4 and the second weight may be 4,regardless of the current block information, the neighbor blockinformation, the quantization parameter (QP), etc.

The first weight and the second weight may be given differentlyaccording to the size of the current block. That is, as the size of thecurrent block increases, the first weight may decrease and the secondweight may increase.

For example, when the size of the current block is 4×4, the first weightmay be 4 and the second weight may be 4.

For example, when the size of the current block is 8×8, the first weightmay be 3 and the second weight may be 5.

For example, when the size of the current block is 16×16, the firstweight may be 2 and the second weight may be 6.

For example, when the size of the current block is 32×32, the firstweight may be 1 and the second weight may be 7.

The first weight and the second weight may be given differentlydepending on whether inter prediction of the current block isbidirectional prediction or unidirectional prediction. That is, when theinter prediction of the current block is bidirectional prediction, alarger second weight and a smaller first weight may be given as comparedto unidirectional prediction.

For example, when the inter prediction mode of the current block is abidirectional prediction mode, the first weight may be 3 and the secondweight may be 5.

For example, when the inter prediction mode of the current block is aunidirectional prediction mode, the first weight may be 5 and the secondweight may be 3.

when the inter prediction mode of the current block is a bidirectionalprediction mode, the first weight may be 2 and the second weight may be6.

For example, when the inter prediction mode of the current block is aunidirectional prediction mode, the first weight may be 6 and the secondweight may be 2.

The first weight and the second weight may be given differentlyaccording to the quantization parameter of the current block. As thequantization parameter of the current block increases, the second weightmay increase and the first weight may decrease.

For example, when the quantization parameter of the current block is 26or less, the first weight may be 6 and the second weight may be 2.

For example, when the quantization parameter of the current block is 27or more and 31 or less, the first weight may be 5 and the second weightmay be 3.

For example, when the quantization parameter of the current block is 32or more and 36 or less, the first weight may be 3 and the second weightmay be 5.

when the quantization parameter of the current block is 37 or more, thefirst weight may be 2 and the second weight may be 6.

For example, after encoding is performed using several weight candidatevalues, an optimal weight may be selected and used through adistortion-optimization process. At this time, the total number ofweight candidate values may be N and N may be an arbitrary positiveinteger of 0 or more. The weight candidate values are as follows.

-   -   {−2:10}, {3:5}, {4:4}, {5:3}, {10:−2}

At this time, the weight value may mean {the first weight: the secondweight}.

The weight selected from among the weight candidate values may beentropy-encoded/decoded in units of pictures/slices/tilegroups/tiles/CTUs/blocks.

For example, after encoding is performed using several weight candidatevalues, an optimal weight may be selected and used through adistortion-optimization process. At this time, the total number ofweight candidate values may be N and N may be an arbitrary positiveinteger of 0 or more. The weight candidate values are as follows. Theweight selected from among the weight candidate values may beentropy-encoded/decoded in units of pictures/slices/tilegroups/tiles/CTUs/blocks.

-   -   {2:6}, {3:5}, {4:4}, {5:3}, {6:2}

At this time, the weight value may mean {the first weight: the secondweight}.

For example, after encoding is performed using several weight candidatevalues, an optimal weight may be selected and used through adistortion-optimization process. At this time, the total number ofweight candidate values may be N and N may be an arbitrary positiveinteger of 0 or more. The weight candidate values are as follows. Theweight selected from among the weight candidate values may beentropy-encoded/decoded in units of pictures/slices/tilegroups/tiles/CTUs/blocks.

-   -   {1:7}, {2:6}, {3:5}, {4:4}, {5:3}, {6:2}, {7:1}

At this time, the weight value may mean {the first weight: the secondweight}.

The first weight and the second weight may be given differentlyaccording to the intra prediction mode of the current block.

For example, when the intra prediction mode of the current block is aPlanar mode or a DC mode, the first weight may be 5 and the secondweight may be 3.

For example, when the intra prediction mode of the current block is aPlanar mode or a DC mode, the first weight may be 6 and the secondweight may be 2.

For example, when the intra prediction mode of the current block is aHorizontal mode or a Vertical mode, the first weight may be 3 and thesecond weight may be 5.

For example, when the intra prediction mode of the current block is aHorizontal mode or a Vertical mode, the first weight may be 2 and thesecond weight may be 6.

For example, when the intra prediction mode of the current block is adirectional mode excluding the Horizontal mode and the Vertical mode,the first weight may be 5 and the second weight may be 3.

For example, when the intra prediction mode of the current block is adirectional mode excluding the Horizontal mode and the Vertical mode,the first weight may be 6 and the second weight may be 2.

For example, when the first weight and the second weight of the leftneighbor block and the top neighbor block are the same regardless of thelocation of the sample, the first weight of the current block may be anaverage of the first weight of the left neighbor block and the firstweight of the top neighbor block, and the second weight of the currentblock may be an average of the second weight of the left neighbor blockand the second weight of the top neighbor block.

For example, the first weight may be given according to the width andheight of the current block through Table 4. The second weight may be(8-the first weight). At this time, width may mean the width of thecurrent block and height may mean the height of the current block.

TABLE 4 width, width, width, width, height == 8 height == 16 height ==32 height == 64 2 3 5 6

The first weight and the second weight may be given differentlyaccording to the number of intra prediction blocks or ratio of intraprediction blocks to the N neighbor blocks adjacent to the currentblock.

At this time, the neighbor blocks adjacent to the current block may meanat least one of the top, bottom, right, top left, top right or bottomleft block with a location difference of N pixels from the boundary ofthe current block. N may be a positive integer value including 0. FIG.11 is a view showing the location of the neighbor block. A to I may meanthe neighbor blocks adjacent to the current block.

For example, when both the top right block and the bottom left block areintra prediction blocks, the first weight may be a multiple of 3 and thesecond weight may be a multiple of 1.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 .

The first weight of a multiple of 3 and the second weight of a multipleof 1 may mean (3:1), (6:2), (9:3), etc.

For example, when one of the top right block and the bottom left blockis an intra prediction block, the first weight may be a multiple of 2and the second weight may be a multiple of 2.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 .

The first weight of a multiple of 2 and the second weight of a multipleof 2 may mean (2:2), (4:4), (6:6), etc.

For example, when both the top right block and the bottom left block arenot intra prediction blocks, the first weight may be a multiple of 1 andthe second weight may be a multiple of 3.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 3 may mean (1:3), (2:6), (3:9), etc.

For example, when both the top left block and the left block are intraprediction blocks, the first weight may be a multiple of 3 and thesecond weight may be a multiple of 1.

At this time, the top left block may mean A or B and the left block maymean A or F in FIG. 11 .

The first weight of a multiple of 3 and the second weight of a multipleof 1 may mean (3:1), (6:2), (9:3), etc.

For example, when one of the top left block and the left block is anintra prediction block, the first weight may be a multiple of 2 and thesecond weight may be a multiple of 2.

At this time, the top left block may mean A or B and the left block maymean A or F in FIG. 11 .

The first weight of a multiple of 2 and the second weight of a multipleof 2 may mean (2:2), (4:4), (6:6), etc.

For example, when both the top left block and the left block are notintra prediction blocks, the first weight may be a multiple of 1 and thesecond weight may be a multiple of 3.

At this time, the top left block may mean A or B and the left block maymean A or F in FIG. 11 .

The first weight of a multiple of 2 and the second weight of a multipleof 2 may mean (1:3), (2:6), (3:9), etc.

For example, when both the top center block and the left center blockare intra prediction blocks, the first weight may be a multiple of 3 andthe second weight may be a multiple of 1.

At this time, the top center block may mean C and the left center blockmay mean G in FIG. 11 .

The first weight of a multiple of 3 and the second weight of a multipleof 1 may mean (3:1), (6:2), (9:3), etc.

For example, when one of the top center block and the left center blockis an intra prediction block, the first weight may be a multiple of 2and the second weight may be a multiple of 2.

At this time, the top center block may mean C and the left center blockmay mean G in FIG. 11 .

The first weight of a multiple of 2 and the second weight of a multipleof 2 may mean (2:2), (4:4), (6:6), etc.

For example, when both the top center block and the left center blockare not intra prediction blocks, the first weight may be a multiple of 1and the second weight may be a multiple of 3.

At this time, the top center block may mean C and the left center blockmay mean G in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 3 may mean (1:3), (2:6), (3:9), etc.

For example, when three or more of the top right block, the bottom leftblock, the top center block and the left center block are intraprediction blocks, the first weight may be a multiple of 3 and thesecond weight may be a multiple of 1.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top center block may mean C andthe left center block may mean G in FIG. 11 .

The first weight of a multiple of 3 and the second weight of a multipleof 1 may mean (3:1), (6:2), (9:3), etc.

For example, when two of the top right block, the bottom left block, thetop center block and the left center block are intra prediction blocks,the first weight may be a multiple of 2 and the second weight may be amultiple of 2.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top center block may mean C andthe left center block may mean G in FIG. 11 .

The first weight of a multiple of 2 and the second weight of a multipleof 2 may mean (2:2), (4:4), (6:6), etc.

For example, when one or less of the top right block, the bottom leftblock, the top center block and the left center block are an intraprediction block, the first weight may be a multiple of 1 and the secondweight may be a multiple of 3.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top center block may mean C andthe left center block may mean G in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 3 may mean (1:3), (2:6), (3:9), etc.

For example, when three or more of the top right block, the bottom leftblock, the top center block and the left center block are intraprediction blocks, the first weight may be a multiple of 3 and thesecond weight may be a multiple of 1.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top center block may mean C andthe left center block may mean G in FIG. 11 .

The first weight of a multiple of 3 and the second weight of a multipleof 1 may mean (3:1), (6:2), (9:3), etc.

For example, when two of the top right block, the bottom left block, thetop center block and the left center block are intra prediction blocks,the first weight may be a multiple of 2 and the second weight may be amultiple of 2.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top center block may mean C andthe left center block may mean G in FIG. 11 .

The first weight of a multiple of 2 and the second weight of a multipleof 2 may mean (2:2), (4:4), (6:6), etc.

For example, when one or less of the top right block, the bottom leftblock, the top center block and the left center block are an intraprediction block, the first weight may be a multiple of 1 and the secondweight may be a multiple of 3.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top center block may mean C andthe left center block may mean G in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 3 may mean (1:3), (2:6), (3:9), etc.

For example, when three or more of the top right block, the bottom leftblock, the top left block and the left block are intra predictionblocks, the first weight may be a multiple of 3 and the second weightmay be a multiple of 1.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top left block may mean A or Band the left block may mean A or F in FIG. 11 .

The first weight of a multiple of 3 and the second weight of a multipleof 1 may mean (3:1), (6:2), (9:3), etc. For example, when two of the topright block, the bottom left block, the top left block and the leftblock are intra prediction blocks, the first weight may be a multiple of2 and the second weight may be a multiple of 2.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top left block may mean A or Band the left block may mean A or F in FIG. 11 .

The first weight of a multiple of 2 and the second weight of a multipleof 2 may mean (2:2), (4:4), (6:6), etc.

For example, when one or less of the top right block, the bottom leftblock, the top left block and the left block is an intra predictionblock, the first weight may be a multiple of 1 and the second weight maybe a multiple of 3.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top left block may mean A or Band the left block may mean A or F in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 3 may mean (1:3), (2:6), (3:9), etc.

For example, when both the top right block and the bottom left block areintra prediction blocks, the first weight may be a multiple of 7 and thesecond weight may be a multiple of 1.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 .

The first weight of a multiple of 7 and the second weight of a multipleof 1 may mean (7:1), (14:2), (21:3), etc.

For example, when one of the top right block and the bottom left blockis an intra prediction block, the first weight may be a multiple of 4and the second weight may be a multiple of 4.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 .

The first weight of a multiple of 4 and the second weight of a multipleof 4 may mean (4:4), (8:8), (12:12), etc.

For example, when both the top right block and the bottom left block arenot intra prediction blocks, the first weight may be a multiple of 1 andthe second weight may be a multiple of 7.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 7 may mean (1:7), (2:14), (3:21), etc.

For example, when both the top left block and the left block are intraprediction blocks, the first weight may be a multiple of 7 and thesecond weight may be a multiple of 1.

At this time, the top left block may mean A or B and the left block maymean A or F in FIG. 11 .

The first weight of a multiple of 7 and the second weight of a multipleof 1 may mean (7:1), (14:2), (21:3), etc.

For example, when one of the top left block and the left block is anintra prediction block, the first weight may be a multiple of 4 and thesecond weight may be a multiple of 4.

At this time, the top left block may mean A or B and the left block maymean A or F in FIG. 11 .

The first weight of a multiple of 4 and the second weight of a multipleof 4 may mean (4:4), (8:8), (12:12), etc.

For example, when both the top left block and the left block are notintra prediction blocks, the first weight may be a multiple of 1 and thesecond weight may be a multiple of 7.

At this time, the top left block may mean A or B and the left block maymean A or F in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 7 may mean (1:7), (2:14), (3:21), etc.

For example, when both the top center block and the left center blockare intra prediction blocks, the first weight may be a multiple of 7 andthe second weight may be a multiple of 1.

At this time, the top center block may mean C and the left center blockmay mean G in FIG. 11 .

The first weight of a multiple of 7 and the second weight of a multipleof 1 may mean (7:1), (14:2), (21:3), etc.

For example, when one of the top center block and the left center blockis an intra prediction block, the first weight may be a multiple of 4and the second weight may be a multiple of 4.

At this time, the top center block may mean C and the left center blockmay mean G in FIG. 11 .

The first weight of a multiple of 4 and the second weight of a multipleof 4 may mean (4:4), (8:8), (12:12), etc.

For example, when both the top center block and the left center blockare not intra prediction blocks, the first weight may be a multiple of 1and the second weight may be a multiple of 7.

At this time, the top center block may mean C and the left center blockmay mean G in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 7 may mean (1:7), (2:14), (3:21), etc.

For example, when three or more of the top right block, the bottom leftblock, the top center block and the left center block are intraprediction blocks, the first weight may be a multiple of 7 and thesecond weight may be a multiple of 1.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top center block may mean C andthe left center block may mean G in FIG. 11 .

The first weight of a multiple of 7 and the second weight of a multipleof 1 may mean (7:1), (14:2), (21:3), etc.

For example, when two of the top right block, the bottom left block, thetop center block and the left center block are intra prediction blocks,the first weight may be a multiple of 4 and the second weight may be amultiple of 4.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top center block may mean C andthe left center block may mean G in FIG. 11 .

The first weight of a multiple of 4 and the second weight of a multipleof 4 may mean (4:4), (8:8), (12:12), etc.

For example, when one or less of the top right block, the bottom leftblock, the top center block and the left center block is an intraprediction block, the first weight may be a multiple of 1 and the secondweight may be a multiple of 7.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top center block may mean C andthe left center block may mean G in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 7 may mean (1:7), (2:14), (3:21), etc.

For example, when three or more of the top right block, the bottom leftblock, the top left block and the left block are intra predictionblocks, the first weight may be a multiple of 7 and the second weightmay be a multiple of 1.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top left block may mean A or Band the left block may mean A or F in FIG. 11 .

The first weight of a multiple of 7 and the second weight of a multipleof 1 may mean (7:1), (14:2), (21:3), etc.

For example, when two of the top right block, the bottom left block, thetop left block and the left block are intra prediction blocks, the firstweight may be a multiple of 4 and the second weight may be a multiple of4.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top left block may mean A or Band the left block may mean A or F in FIG. 11 .

The first weight of a multiple of 4 and the second weight of a multipleof 4 may mean (4:4), (8:8), (12:12), etc.

For example, when one or less of the top right block, the bottom leftblock, the top left block and the left block is an intra predictionblock, the first weight may be a multiple of 1 and the second weight maybe a multiple of 7.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top left block may mean A or Band the left block may mean A or F in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 7 may mean (1:7), (2:14), (3:21), etc.

At this time, the multiple of 1 may mean 1*n, the multiple of 2 may mean2*n, the multiple of 3 may mean 3*n, and the multiple of 7 may mean 7*n.n may be an arbitrary integer.

The first weight and the second weight may be given differentlyaccording to the number of blocks each having a non-directionalprediction mode or ratio of blocks each having a non-directionalprediction mode to the N neighbor blocks adjacent to the current blocks.

At this time, the neighbor blocks adjacent to the current block may meanat least one of the top, bottom, right, top left, top right or bottomleft block with a location difference of N pixels from the boundary ofthe current block. N may be a positive integer value including 0. FIG.11 is a view showing the location of the neighbor block. A to I may meanthe neighbor blocks adjacent to the current block.

In addition, the non-directional prediction mode may mean a PLANAR modeor a DC mode.

For example, when both the top right block and the bottom left block areintra prediction blocks each having a non-directional prediction mode,the first weight may be a multiple of 3 and the second weight may be amultiple of 1.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 .

The first weight of a multiple of 3 and the second weight of a multipleof 1 may mean (3:1), (6:2), (9:3), etc.

For example, when one of the top right block and the bottom left blockis an intra prediction block having a non-directional prediction mode,the first weight may be a multiple of 2 and the second weight may be amultiple of 2.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 .

The first weight of a multiple of 2 and the second weight of a multipleof 2 may mean (2:2), (4:4), (6:6), etc.

For example, when both the top right block and the bottom left block arenot intra prediction blocks each having a non-directional predictionmode, the first weight may be a multiple of 1 and the second weight maybe a multiple of 3.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 3 may mean (1:3), (2:6), (3:9), etc.

For example, when both the top left block and the left block are intraprediction blocks each having a non-directional prediction mode, thefirst weight may be a multiple of 3 and the second weight may be amultiple of 1.

At this time, the top left block may mean A or B and the left block maymean A or F in FIG. 11 .

The first weight of a multiple of 3 and the second weight of a multipleof 1 may mean (3:1), (6:2), (9:3), etc.

For example, when one of the top left block and the left block is anintra prediction block having a non-directional prediction mode, thefirst weight may be a multiple of 2 and the second weight may be amultiple of 2.

At this time, the top left block may mean A or B and the left block maymean A or F in FIG. 11 .

The first weight of a multiple of 2 and the second weight of a multipleof 2 may mean (2:2), (4:4), (6:6), etc.

For example, when both the top left block and the left block are notintra prediction blocks each having a non-directional prediction mode,the first weight may be a multiple of 1 and the second weight may be amultiple of 3.

At this time, the top left block may mean A or B and the left block maymean A or F in FIG. 11 .

The first weight of a multiple of 2 and the second weight of a multipleof 2 may mean (1:3), (2:6), (3:9), etc.

For example, when both the top center block and the left center blockare intra prediction blocks each having a non-directional predictionmode, the first weight may be a multiple of 3 and the second weight maybe a multiple of 1.

At this time, the top center block may mean C and the left center blockmay mean G in FIG. 11 .

The first weight of a multiple of 3 and the second weight of a multipleof 1 may mean (3:1), (6:2), (9:3), etc.

For example, when one of the top center block and the left center blockis an intra prediction block having a non-directional prediction mode,the first weight may be a multiple of 2 and the second weight may be amultiple of 2.

At this time, the top center block may mean C and the left center blockmay mean G in FIG. 11 .

The first weight of a multiple of 2 and the second weight of a multipleof 2 may mean (2:2), (4:4), (6:6), etc.

For example, when both the top center block and the left center blockare not intra prediction blocks each having a non-directional predictionmode, the first weight may be a multiple of 1 and the second weight maybe a multiple of 3.

At this time, the top center block may mean C and the left center blockmay mean G in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 3 may mean (1:3), (2:6), (3:9), etc.

For example, when three or more of the top right block, the bottom leftblock, the top center block and the left center block are intraprediction blocks each having a non-directional prediction mode, thefirst weight may be a multiple of 3 and the second weight may be amultiple of 1.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top center block may mean C andthe left center block may mean G in FIG. 11 .

The first weight of a multiple of 3 and the second weight of a multipleof 1 may mean (3:1), (6:2), (9:3), etc.

For example, when two of the top right block, the bottom left block, thetop center block and the left center block are intra prediction blockseach having a non-directional prediction mode, the first weight may be amultiple of 2 and the second weight may be a multiple of 2.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top center block may mean C andthe left center block may mean G in FIG. 11 .

The first weight of a multiple of 2 and the second weight of a multipleof 2 may mean (2:2), (4:4), (6:6), etc.

For example, when one or less of the top right block, the bottom leftblock, the top center block and the left center block is an intraprediction block having a non-directional prediction mode, the firstweight may be a multiple of 1 and the second weight may be a multiple of3.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top center block may mean C andthe left center block may mean G in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 3 may mean (1:3), (2:6), (3:9), etc.

For example, when three or more of the top right block, the bottom leftblock, the top left block and the left block are intra prediction blockseach having a non-directional prediction mode, the first weight may be amultiple of 3 and the second weight may be a multiple of 1.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top left block may mean A or Band the left block may mean A or F in FIG. 11 .

The first weight of a multiple of 3 and the second weight of a multipleof 1 may mean (3:1), (6:2), (9:3), etc.

For example, when two of the top right block, the bottom left block, thetop left block and the left block are intra prediction blocks eachhaving a non-directional prediction mode, the first weight may be amultiple of 2 and the second weight may be a multiple of 2.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top left block may mean A or Band the left block may mean A or F in FIG. 11 .

The first weight of a multiple of 2 and the second weight of a multipleof 2 may mean (2:2), (4:4), (6:6), etc.

For example, when one or less of the top right block, the bottom leftblock, the top left block and the left block are intra prediction blockshaving a non-directional prediction mode, the first weight may be amultiple of 1 and the second weight may be a multiple of 3.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top left block may mean A or Band the left block may mean A or F in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 3 may mean (1:3), (2:6), (3:9), etc.

At this time, the multiple of 1 may mean 1*n, the multiple of 2 may mean2*n, the multiple of 3 may mean 3*n, and the multiple of 7 may mean 7*n.n may be an arbitrary integer.

For example, when both the top right block and the bottom left block areintra prediction blocks each having a non-directional prediction mode,the first weight may be a multiple of 7 and the second weight may be amultiple of 1.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 .

The first weight of a multiple of 7 and the second weight of a multipleof 1 may mean (7:1), (14:2), (21:3), etc.

For example, when one of the top right block and the bottom left blockis an intra prediction blocks having a non-directional prediction mode,the first weight may be a multiple of 4 and the second weight may be amultiple of 4.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 .

The first weight of a multiple of 4 and the second weight of a multipleof 4 may mean (4:4), (8:8), (12:12), etc.

For example, when both the top right block and the bottom left block arenot intra prediction blocks each having a non-directional predictionmode, the first weight may be a multiple of 1 and the second weight maybe a multiple of 7.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 7 may mean (1:7), (2:14), (3:21), etc.

For example, when both the top left block and the left block are intraprediction blocks each having a non-directional prediction mode, thefirst weight may be a multiple of 7 and the second weight may be amultiple of 1.

At this time, the top left block may mean A or B and the left block maymean A or F in FIG. 11 .

The first weight of a multiple of 7 and the second weight of a multipleof 1 may mean (7:1), (14:2), (21:3), etc.

For example, when one of the top left block and the left block is anintra prediction blocks having a non-directional prediction mode, thefirst weight may be a multiple of 4 and the second weight may be amultiple of 4.

At this time, the top left block may mean A or B and the left block maymean A or F in FIG. 11 .

The first weight of a multiple of 4 and the second weight of a multipleof 4 may mean (4:4), (8:8), (12:12), etc.

For example, when both the top left block and the left block are notintra prediction blocks each having a non-directional prediction mode,the first weight may be a multiple of 1 and the second weight may be amultiple of 7.

At this time, the top left block may mean A or B and the left block maymean A or F in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 7 may mean (1:7), (2:14), (3:21), etc.

For example, when both the top center block and the left center blockare intra prediction blocks each having a non-directional predictionmode, the first weight may be a multiple of 7 and the second weight maybe a multiple of 1.

At this time, the top center block may mean C and the left center blockmay mean G in FIG. 11 .

The first weight of a multiple of 7 and the second weight of a multipleof 1 may mean (7:1), (14:2), (21:3), etc.

For example, when one of the top center block and the left center blockis an intra prediction blocks having a non-directional prediction mode,the first weight may be a multiple of 4 and the second weight may be amultiple of 4.

At this time, the top center block may mean C and the left center blockmay mean G in FIG. 11 .

The first weight of a multiple of 4 and the second weight of a multipleof 4 may mean (4:4), (8:8), (12:12), etc.

For example, when both the top center block and the left center blockare not intra prediction blocks each having a non-directional predictionmode, the first weight may be a multiple of 1 and the second weight maybe a multiple of 7.

At this time, the top center block may mean C and the left center blockmay mean G in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 7 may mean (1:7), (2:14), (3:21), etc.

For example, when three or more of the top right block, the bottom leftblock, the top center block and the left center block are intraprediction blocks each having a non-directional prediction mode, thefirst weight may be a multiple of 7 and the second weight may be amultiple of 1.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top center block may mean C andthe left center block may mean G in FIG. 11 .

The first weight of a multiple of 7 and the second weight of a multipleof 1 may mean (7:1), (14:2), (21:3), etc.

For example, when two of the top right block, the bottom left block, thetop center block and the left center block are intra prediction blockseach having a non-directional prediction mode, the first weight may be amultiple of 4 and the second weight may be a multiple of 4.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top center block may mean C andthe left center block may mean G in FIG. 11 .

The first weight of a multiple of 4 and the second weight of a multipleof 4 may mean (4:4), (8:8), (12:12), etc.

For example, when one or less of the top right block, the bottom leftblock, the top center block and the left center block is an intraprediction block having a non-directional prediction mode, the firstweight may be a multiple of 1 and the second weight may be a multiple of7.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top center block may mean C andthe left center block may mean G in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 7 may mean (1:7), (2:14), (3:21), etc.

For example, when three or more of the top right block, the bottom leftblock, the top left block and the left block are intra prediction blockseach having a non-directional prediction mode, the first weight may be amultiple of 7 and the second weight may be a multiple of 1.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top left block may mean A or Band the left block may mean A or F in FIG. 11 .

The first weight of a multiple of 7 and the second weight of a multipleof 1 may mean (7:1), (14:2), (21:3), etc.

For example, when two of the top right block, the bottom left block, thetop left block and the left block are intra prediction blocks eachhaving a non-directional prediction mode, the first weight may be amultiple of 4 and the second weight may be a multiple of 4.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top left block may mean A or Band the left block may mean A or F in FIG. 11 .

The first weight of a multiple of 4 and the second weight of a multipleof 4 may mean (4:4), (8:8), (12:12), etc.

For example, when one or less of the top right block, the bottom leftblock, the top left block and the left block is an intra predictionblock having a non-directional prediction mode, the first weight may bea multiple of 1 and the second weight may be a multiple of 7.

At this time, the top right block may mean D or E and the bottom leftblock may mean H or I in FIG. 11 . The top left block may mean A or Band the left block may mean A or F in FIG. 11 .

The first weight of a multiple of 1 and the second weight of a multipleof 7 may mean (1:7), (2:14), (3:21), etc.

At this time, the multiple of 1 may mean 1*n, the multiple of 2 may mean2*n, the multiple of 3 may mean 3*n, and the multiple of 7 may mean 7*n.n may be an arbitrary integer.

In FIG. 11 , the top block may mean A, B, C, D or E, the top left blockmay mean A, B or F, the top right block may mean D or E, the top centerblock may mean C, the left block may mean A, F, G, H or I, the bottomleft block may mean H or I, and the left center block may mean G.

The final prediction block may be generated through Equation 2 or 3.

predSamplesComb(x,y)=(the first weight*predSamplesIntra(x,y)+the secondweight*predSamplesInter(x,y))>>M  Equation 2

predSamplesComb(x,y)=(the first weight*predSamplesIntra(x,y)+the secondweight*predSamplesInter(x,y)+N)>>M  Equation 3

where, N and M may be positive integers, M of Equation 2 above may be 3,and N and M of Equation 3 above may be 2.

For example, when the sum of the first weight and the second weight is16, M may be 4.

In another example, when the sum of the first weight and the secondweight is 8, M may be 3.

In another example, when the sum of the first weight and the secondweight is 4, M may be 2.

In another example, when the sum of the first weight and the secondweight is 2, M may be 1.

For example, when the value of M is 2, N may be 2.

For example, when the value of M is 3, N may be 4.

The first weight and the second weight may be given differently for eachzone of the current block based on the form of the current block and theintra prediction mode.

For example, when the intra prediction mode of the current block is aPlanar mode or a DC mode or the width or height of the current block isless than 4, as the first weight and the second weight, 4:4 may be givento a zone {circle around (1)}, 4:4 may be given to a zone {circle around(2)}, 4:4 may be given to a zone {circle around (3)}, and 4:4 may begiven to a zone {circle around (4)} in FIGS. 12 and 13 .

For example, when the intra prediction mode of the current block is aHorizontal mode, as the first weight and the second weight, 6:2 may begiven to a zone {circle around (1)}, 5:3 may be given to a zone {circlearound (2)}, 3:5 may be given to a zone {circle around (3)}, and 2:6 maybe given to a zone {circle around (4)} in FIGS. 12 and 13 . At thistime, the mode value of the Horizontal mode may be 18.

For example, when the intra prediction mode of the current block is aVertical mode, as the first weight and the second weight, 6:2 may begiven to a zone {circle around (1)}, 5:3 may be given to a zone {circlearound (2)}, 3:5 may be given to a zone {circle around (3)}, and 2:6 maybe given to a zone {circle around (4)} in FIGS. 12 and 13 . At thistime, the mode value of the Vertical mode may be 50.

For example, when the intra prediction mode of the current block is adirectional mode excluding the Horizontal mode and the Vertical mode andthe weight and height of the current block is greater than 4, as thefirst weight and the second weight, 4:4 may be given to a zone {circlearound (1)}, 4:4 may be given to a zone {circle around (2)}, 4:4 may begiven to a zone {circle around (3)}, and 4:4 may be given to a zone{circle around (4)} in FIGS. 12 and 13 . At this time, the mode value ofthe Horizontal mode may be 18 and the mode value of the Vertical modemay be 50.

For example, when the intra prediction mode of the current block is amode located below the diagonal mode and the width and height of thecurrent block is greater than 4, as the first weight and the secondweight, 6:2 may be given to a zone {circle around (1)}, 6:2 may be givento a zone {circle around (2)}, 2:6 may be given to a zone {circle around(3)}, and 2:6 may be given to a zone {circle around (4)} in FIGS. 12 and13 . At this time, the mode value of the diagonal mode may be 34.

For example, when the intra prediction mode of the current block is adiagonal mode or is a mode located above the diagonal mode and the widthand height of the current block is greater than 4, as the first weightand the second weight, 6:2 may be given to a zone {circle around (1)},6:2 may be given to a zone {circle around (2)}, 2:6 may be given to azone {circle around (3)}, and 2:6 may be given to a zone {circle around(4)} in FIGS. 12 and 13 . At this time, the mode value of the diagonalmode may be 34.

For example, when the intra prediction mode of the current block is amode located below the diagonal mode and the weight and height of thecurrent block is greater than 4, as the first weight and the secondweight, 5:3 may be given to a zone {circle around (1)}, 5:3 may be givento a zone {circle around (2)}, 3:5 may be given to a zone {circle around(3)}, and 3:5 may be given to a zone {circle around (4)} in FIGS. 12 and13 . At this time, the mode value of the diagonal mode may be 34.

For example, when the intra prediction mode of the current block is adiagonal mode or a mode located above the diagonal mode and the weightand height of the current block is greater than 4, as the first weightand the second weight, 5:3 may be given to a zone {circle around (1)},5:3 may be given to a zone {circle around (2)}, 3:5 may be given to azone {circle around (3)}, and 3:5 may be given to a zone {circle around(4)} in FIGS. 12 and 13 . At this time, the mode value of the diagonalmode may be 34.

For example, when the intra prediction mode of the current block is abidirectional prediction mode, as the first weight and the secondweight, 2:6 may be given to a zone {circle around (1)}, 2:6 may be givento a zone {circle around (2)}, 2:6 may be given to a zone {circle around(3)}, and 2:6 may be given to a zone {circle around (4)}in FIGS. 12 and13 .

For example, when the intra prediction mode of the current block is aunidirectional prediction mode, as the first weight and the secondweight, 5:3 may be given to a zone {circle around (1)}, 5:3 may be givento a zone {circle around (2)}, 5:3 may be given to a zone {circle around(3)}, and 5:3 may be given to a zone {circle around (4)} in FIGS. 12 and13 .

The first weight and the second weight may be given differently for eachzone of the current block based on the form of the current block and thequantization parameter.

For example, when the quantization parameter value of the current blockis 26 or less, as the first weight and the second weight, 6:2 may begiven to a zone {circle around (1)}, 6:2 may be given to a zone {circlearound (2)}, 6:2 may be given to a zone {circle around (3)}, and 6:2 maybe given to a zone {circle around (4)} in FIGS. 12 and 13 .

For example, when the quantization parameter value of the current blockis 27 or more and 31 or less, as the first weight and the second weight,5:3 may be given to a zone {circle around (1)}, 5:3 may be given to azone {circle around (2)}, 5:3 may be given to a zone {circle around(3)}, and 5:3 may be given to a zone {circle around (4)} in FIGS. 12 and13 .

For example, when the quantization parameter value of the current blockis 32 or more and 36 or less, as the first weight and the second weight,3:5 may be given to a zone {circle around (1)}, 3:5 may be given to azone {circle around (2)}, 3:5 may be given to a zone {circle around(3)}, and 3:5 may be given to a zone {circle around (4)} in FIGS. 12 and13 .

For example, when the quantization parameter value of the current blockis 37 or more, as the first weight and the second weight, 2:6 may begiven to a zone {circle around (1)}, 2:6 may be given to a zone {circlearound (2)}, 2:6 may be given to a zone {circle around (3)}, and 2:6 maybe given to a zone {circle around (4)} in FIGS. 12 and 13 .

For example, after encoding is performed using several weight candidatevalues, an optimal weight may be selected and used through adistortion-optimization process. In this case, the selected weight maybe signaled from the encoder to the decoder. at this time, the weightcandidate values are as follows.

As the first weight and the second weight, −2:10 may be given to a zone{circle around (1)}, −2:10 may be given to a zone {circle around (2)},−2:10 may be given to a zone {circle around (3)}, and −2:10 may be givento a zone {circle around (4)} in FIGS. 12 and 13 .

As the first weight and the second weight, 3:5 may be given to a zone{circle around (1)}, 3:5 may be given to a zone {circle around (2)}, 3:5may be given to a zone {circle around (3)}, and 3:5 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

As the first weight and the second weight, 4:4 may be given to a zone{circle around (1)}, 4:4 may be given to a zone {circle around (2)}, 4:4may be given to a zone {circle around (3)}, and 4:4 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

As the first weight and the second weight, 5:3 may be given to a zone{circle around (1)}, 5:3 may be given to a zone {circle around (2)}, 5:3may be given to a zone {circle around (3)}, and 5:3 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

As the first weight and the second weight, 10:−2 may be given to a zone{circle around (1)}, 10:−2 may be given to a zone {circle around (2)},10:−2 may be given to a zone {circle around (3)}, and 10:−2 may be givento a zone {circle around (4)} in FIGS. 12 and 13 .

As the first weight and the second weight, 2:6 may be given to a zone{circle around (1)}, 2:6 may be given to a zone {circle around (2)}, 2:6may be given to a zone {circle around (3)}, and 2:6 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

As the first weight and the second weight, 3:5 may be given to a zone{circle around (1)}, 3:5 may be given to a zone {circle around (2)}, 3:5may be given to a zone {circle around (3)}, and 3:5 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

As the first weight and the second weight, 4:4 may be given to a zone{circle around (1)}, 4:4 may be given to a zone {circle around (2)}, 4:4may be given to a zone {circle around (3)}, and 4:4 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

As the first weight and the second weight, 5:3 may be given to a zone{circle around (1)}, 5:3 may be given to a zone {circle around (2)}, 5:3may be given to a zone {circle around (3)}, and 5:3 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

As the first weight and the second weight, 6:2 may be given to a zone{circle around (1)}, 6:2 may be given to a zone {circle around (2)}, 6:2may be given to a zone {circle around (3)}, and 6:2 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

As the first weight and the second weight, 1:7 may be given to a zone{circle around (1)}, 1:7 may be given to a zone {circle around (2)}, 1:7may be given to a zone {circle around (3)}, and 1:7 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

As the first weight and the second weight, 2:6 may be given to a zone{circle around (1)}, 2:6 may be given to a zone {circle around (2)}, 2:6may be given to a zone {circle around (3)}, and 2:6 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

As the first weight and the second weight, 3:5 may be given to a zone{circle around (1)}, 3:5 may be given to a zone {circle around (2)}, 3:5may be given to a zone {circle around (3)}, and 3:5 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

As the first weight and the second weight, 4:4 may be given to a zone{circle around (1)}, 4:4 may be given to a zone {circle around (2)}, 4:4may be given to a zone {circle around (3)}, and 4:4 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

As the first weight and the second weight, 5:3 may be given to a zone{circle around (1)}, 5:3 may be given to a zone {circle around (2)}, 5:3may be given to a zone {circle around (3)}, and 5:3 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

As the first weight and the second weight, 6:2 may be given to a zone{circle around (1)}, 6:2 may be given to a zone {circle around (2)}, 6:2may be given to a zone {circle around (3)}, and 6:2 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

As the first weight and the second weight, 7:1 may be given to a zone{circle around (1)}, 7:1 may be given to a zone {circle around (2)}, 7:1may be given to a zone {circle around (3)}, and 7:1 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

The first weight and the second weight may be given differently for eachzone of the current block based on the number of intra prediction blocksor ratio of intra prediction blocks to the neighbor blocks adjacent tothe current block. At this time, the neighbor blocks adjacent to thecurrent block may mean at least one of the top, bottom, right, top left,top right or bottom left block adjacent to the boundary of the currentblock.

For example, when both the top right block and the bottom left block areintra prediction blocks, as the first weight and the second weight, 3:1may be given to a zone {circle around (1)}, 3:1 may be given to a zone{circle around (2)}, 3:1 may be given to a zone {circle around (3)}, and3:1 may be given to a zone {circle around (4)} in FIGS. 12 and 13 .

For example, when one of the top right block and the bottom left blockis an intra prediction block, as the first weight and the second weight,2:2 may be given to a zone {circle around (1)}, 2:2 may be given to azone {circle around (2)}, 2:2 may be given to a zone 3, and 2:2 may begiven to a zone {circle around (4)} in FIGS. 12 and 13 .

For example, when both the top right block and the bottom left block arenot intra prediction blocks, as the first weight and the second weight,1:3 may be given to a zone {circle around (1)}, 1:3 may be given to azone {circle around (2)}, 1:3 may be given to a zone {circle around(3)}, and 1:3 may be given to a zone {circle around (4)} in FIGS. 12 and13 .

For example, when both the top left block and the left block are intraprediction blocks, as the first weight and the second weight, 3:1 may begiven to a zone {circle around (1)}, 3:1 may be given to a zone {circlearound (2)}, 3:1 may be given to a zone {circle around (3)}, and 3:1 maybe given to a zone {circle around (4)} in FIGS. 12 and 13 .

For example, when one of the top left block and the left block is anintra prediction block, as the first weight and the second weight, 2:2may be given to a zone {circle around (1)}, 2:2 may be given to a zone{circle around (2)}, 2:2 may be given to a zone {circle around (3)}, and2:2 may be given to a zone {circle around (4)} in FIGS. 12 and 13 .

For example, when both the top left block and the left block are notintra prediction blocks, as the first weight and the second weight, 1:3may be given to a zone {circle around (1)}, 1:3 may be given to a zone{circle around (2)}, 1:3 may be given to a zone {circle around (3)}, and1:3 may be given to a zone {circle around (4)} in FIGS. 12 and 13 .

For example, when both the top center block and the left center blockare intra prediction blocks, as the first weight and the second weight,3:1 may be given to a zone {circle around (1)}, 3:1 may be given to azone {circle around (2)}, 3:1 may be given to a zone {circle around(3)}, and 3:1 may be given to a zone {circle around (4)} in FIGS. 12 and13 .

For example, when one of the top center block and the left center blockis an intra prediction block, as the first weight and the second weight,2:2 may be given to a zone {circle around (1)}, 2:2 may be given to azone {circle around (2)}, 2:2 may be given to a zone {circle around(3)}, and 2:2 may be given to a zone {circle around (4)} in FIGS. 12 and13 .

For example, when both the top center block and the left center blockare not intra prediction blocks, as the first weight and the secondweight, 1:3 may be given to a zone {circle around (1)}, 1:3 may be givento a zone {circle around (2)}, 1:3 may be given to a zone {circle around(3)}, and 1:3 may be given to a zone {circle around (4)} in FIGS. 12 and13 .

For example, when three or more of the top right block, the bottom leftblock, the top center block and the left center block are intraprediction blocks, as the first weight and the second weight, 3:1 may begiven to a zone {circle around (1)}, 3:1 may be given to a zone {circlearound (2)}, 3:1 may be given to a zone {circle around (3)}, and 3:1 maybe given to a zone {circle around (4)} in FIGS. 12 and 13 .

For example, when two of the top right block, the bottom left block, thetop center block and the left center block are intra prediction blocks,as the first weight and the second weight, 2:2 may be given to a zone{circle around (1)}, 2:2 may be given to a zone {circle around (2)}, 2:2may be given to a zone {circle around (3)}, and 2:2 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

For example, when one or less of the top right block, the bottom leftblock, the top center block and the left center block are intraprediction blocks, as the first weight and the second weight, 1:3 may begiven to a zone {circle around (1)}, 1:3 may be given to a zone {circlearound (2)}, 1:3 may be given to a zone {circle around (3)}, and 1:3 maybe given to a zone {circle around (4)} in FIGS. 12 and 13 .

For example, when three or more of the top right block, the bottom leftblock, the top left block and the left block are intra predictionblocks, as the first weight and the second weight, 3:1 may be given to azone {circle around (1)}, 3:1 may be given to a zone {circle around(2)}, 3:1 may be given to a zone {circle around (3)}, and 3:1 may begiven to a zone {circle around (4)} in FIGS. 12 and 13 .

When two of the top right block, the bottom left block, the top leftblock and the left block are intra prediction blocks, as the firstweight and the second weight, 2:2 may be given to a zone {circle around(1)}, 2:2 may be given to a zone {circle around (2)}, 2:2 may be givento a zone {circle around (3)}, and 2:2 may be given to a zone {circlearound (4)} in FIGS. 12 and 13 .

For example, when one or less of the top right block, the bottom leftblock, the top left block and the left block is an intra predictionblock, as the first weight and the second weight, 1:3 may be given to azone {circle around (1)}, 1:3 may be given to a zone {circle around(2)}, 1:3 may be given to a zone {circle around (3)}, and 1:3 may begiven to a zone {circle around (4)} in FIGS. 12 and 13 .

The first weight and the second weight may be given differently for eachzone of the current block based on the intra prediction mode of thecurrent block.

For example, when the intra prediction mode of the current block is aPlanar mode or a DC mode, as the first weight and the second weight, 5:3may be given to a zone {circle around (1)}, 5:3 may be given to a zone{circle around (2)}, 5:3 may be given to a zone {circle around (3)}, and5:3 may be given to a zone {circle around (4)} in FIGS. 12 and 13 .

For example, when the intra prediction mode of the current block is aPlanar mode or a DC mode, as the first weight and the second weight, 6:2may be given to a zone {circle around (1)}, 6:2 may be given to a zone{circle around (2)}, 6:2 may be given to a zone {circle around (3)}, and6:2 may be given to a zone {circle around (4)} in FIGS. 12 and 13 .

For example, when the intra prediction mode of the current block is aHorizontal mode or a Vertical mode, as the first weight and the secondweight, 3:5 may be given to a zone {circle around (1)}, 3:5 may be givento a zone {circle around (2)}, 3:5 may be given to a zone {circle around(3)}, and 3:5 may be given to a zone {circle around (4)} in FIGS. 12 and13 .

For example, when the intra prediction mode of the current block is aHorizontal mode or a Vertical mode, as the first weight and the secondweight, 2:6 may be given to a zone {circle around (1)}, 2:6 may be givento a zone {circle around (2)}, 2:6 may be given to a zone {circle around(3)}, and 2:6 may be given to a zone {circle around (4)} in FIGS. 12 and13 .

For example, the intra prediction mode of the current block is adirectional mode excluding a Horizontal mode and a Vertical mode, as thefirst weight and the second weight, 5:3 may be given to a zone {circlearound (1)}, 5:3 may be given to a zone {circle around (2)}, 5:3 may begiven to a zone {circle around (3)}, and 5:3 may be given to a zone{circle around (4)} in FIGS. 12 and 13 .

For example, the intra prediction mode of the current block is adirectional mode excluding a Horizontal mode and a Vertical mode, as thefirst weight and the second weight, 6:2 may be given to a zone {circlearound (1)}, 6:2 may be given to a zone {circle around (2)}, 6:2 may begiven to a zone {circle around (3)}, and 6:2 may be given to a zone{circle around (4)} in FIGS. 12 and 13 .

The first weight and the second weight may be given differently for eachzone of the current block based on the first weight and the secondweight of each zone of at least one neighbor block of the current block.

For example, when the first weights of the zone {circle around (1)}, thezone {circle around (2)}, the zone {circle around (3)} and the zone{circle around (4)} of the left neighbor block and the top neighborblock are the same and the second weights of the zone {circle around(1)}, the zone {circle around (2)}, the zone {circle around (3)} and thezone {circle around (4)} are the same, the first weight of the currentblock may be an average of the first weight of the left neighbor blockand the first weight of the top neighbor block, and the second weight ofthe current block may be an average of the second weight of the leftneighbor block and the second weight of the top neighbor block.

The first weight and the second weight may be given differently for eachzone of the current block based on the width and height of the currentblock.

For example, when the width and height of the current block is 8, as thefirst weight and the second weight, 2:6 may be given to a zone {circlearound (1)}, 2:6 may be given to a zone {circle around (2)}, 2:6 may begiven to a zone {circle around (3)}, and 2:6 may be given to a zone{circle around (4)} in FIGS. 12 and 13 .

For example, when the width and height of the current block is 16, asthe first weight and the second weight, 3:5 may be given to a zone{circle around (1)}, 3:5 may be given to a zone {circle around (2)}, 3:5may be given to a zone {circle around (3)}, and 3:5 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

For example, when the width and height of the current block is 32, asthe first weight and the second weight, 5:3 may be given to a zone{circle around (1)}, 5:3 may be given to a zone {circle around (2)}, 5:3may be given to a zone {circle around (3)}, and 5:3 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

For example, when the width and height of the current block is 64, asthe first weight and the second weight, 6:2 may be given to a zone{circle around (1)}, 6:2 may be given to a zone {circle around (2)}, 6:2may be given to a zone {circle around (3)}, and 6:2 may be given to azone {circle around (4)} in FIGS. 12 and 13 .

At this time, when the same weight is assigned to the zones {circlearound (1)}, {circle around (2)}, {circle around (3)}and {circle around(4)} of FIGS. 12 and 13 , the same weight may be assigned to one blockas shown in FIG. 14 .

In the embodiment, the weight may mean (the first weight:the secondweight).

In a combination of an intra prediction block and an inter predictionblock, the final prediction block may be generated by partitioning thecurrent block in units of N×N blocks and giving different weights. Here,N may mean an arbitrary positive integer.

FIG. 15 shows an example in which the size of a block is 8×8 and N is 4.Referring to FIG. 15 , the final prediction block may be generated inorder of A, B, C and D.

When the final prediction block of A is generated, the final predictionblock may be generated thorough different weighted sum using Equation 2or Equation 3 depending on whether intra prediction is performed withrespect to the neighbor block on the top right or bottom left of A.Here, the top right or bottom left of A may be replaced with thelocations A to I of FIG. 11 .

For example, intra prediction may be performed with respect to theneighbor block on the top right of A and intra prediction may beperformed with respect to the neighbor block on the bottom left of A. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (3, 1), (7, 1), (15, 1), or the first weight and thesecond weight, a sum of which is a multiple of 2.

For example, intra prediction may be performed with respect to theneighbor block on the top right of A and inter prediction may beperformed with respect to the neighbor block on the bottom left of A. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 1), (2, 2), (4, 4) or a first weight and a secondweight each having 1 or a multiple of 2.

For example, inter prediction may be performed with respect to theneighbor block on the top right of A and intra prediction may beperformed with respect to the neighbor block on the bottom left of A. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 1), (2, 2), (4, 4) or a first weight and a secondweight each having 1 or a multiple of 2.

For example, inter prediction may be performed with respect to theneighbor block of the top right of A and inter prediction may beperformed with respect to the neighbor block on the bottom left of A. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 3), (1, 7), (1, 15) or a first weight and a secondweight, a sum of which is a multiple of 2.

When the final prediction block of B is generated, the final predictionblock may be generated thorough different weighted sum using Equation 2or Equation 3 depending on whether intra prediction is performed withrespect to the neighbor block on the top right or bottom left (the leftcenter of the neighbor block) of B. Here, the top right or bottom leftof B may be replaced with the locations A to I of FIG. 11 .

For example, intra prediction may be performed with respect to theneighbor block on the top right of B and intra prediction may beperformed with respect to the neighbor block on the bottom left of B. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be may be (3, 1), (7, 1), (15, 1), or the first weightand the second weight, a sum of which is a multiple of 2.

For example, intra prediction may be performed with respect to theneighbor block on the top right of B and inter prediction may beperformed with respect to the neighbor block on the bottom left of B. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 1), (2, 2), (4, 4) or a first weight and a secondweight each having 1 or a multiple of 2.

For example, inter prediction may be performed with respect to theneighbor block on the top right of B and intra prediction may beperformed with respect to the neighbor block on the bottom left of B. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 1), (2, 2), (4, 4) or a first weight and a secondweight each having 1 or a multiple of 2.

For example, inter prediction may be performed with respect to theneighbor block of the top right of B and inter prediction may beperformed with respect to the neighbor block on the bottom left of B. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 3), (1, 7), (1, 15) or a first weight and a secondweight, a sum of which is a multiple of 2.

When the final prediction block of C is generated, the final predictionblock may be generated thorough different weighted sum using Equation 2or Equation 3 depending on whether intra prediction is performed withrespect to the neighbor block on the top right (the top center of theneighbor block) or bottom left side of C. Here, the top right or bottomleft of C may be replaced with the locations A to I of FIG. 11 .

For example, intra prediction may be performed with respect to theneighbor block on the top right of C and intra prediction may beperformed with respect to the neighbor block on the bottom left of C. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be may be (3, 1), (7, 1), (15, 1), or the first weightand the second weight, a sum of which is a multiple of 2.

For example, intra prediction may be performed with respect to theneighbor block on the top right of C and inter prediction may beperformed with respect to the neighbor block on the bottom left of C. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 1), (2, 2), (4, 4) or a first weight and a secondweight each having 1 or a multiple of 2.

For example, inter prediction may be performed with respect to theneighbor block on the top right of C and intra prediction may beperformed with respect to the neighbor block on the bottom left of C. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 1), (2, 2), (4, 4) or a first weight and a secondweight each having 1 or a multiple of 2.

For example, inter prediction may be performed with respect to theneighbor block of the top right of C and inter prediction may beperformed with respect to the neighbor block on the bottom left of C. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 3), (1, 7), (1, 15) or a first weight and a secondweight, a sum of which is a multiple of 2.

When the final prediction block of D is generated, the final predictionblock may be generated thorough different weighted sum using Equation 2or Equation 3 depending on whether intra prediction is performed withrespect to the neighbor block on the top right (the top center of theneighbor block) or bottom left of C. Here, the top right or bottom leftof D may be replaced with the locations A to I of FIG. 11 .

For example, intra prediction may be performed with respect to theneighbor block on the top right of D and intra prediction may beperformed with respect to the neighbor block on the bottom left of D. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be may be (3, 1), (7, 1), (15, 1), or the first weightand the second weight, a sum of which is a multiple of 2.

For example, intra prediction may be performed with respect to theneighbor block on the top right of D and inter prediction may beperformed with respect to the neighbor block on the bottom left of D. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 1), (2, 2), (4, 4) or a first weight and a secondweight each having 1 or a multiple of 2.

For example, inter prediction may be performed with respect to theneighbor block on the top right of D and intra prediction may beperformed with respect to the neighbor block on the bottom left of D. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 1), (2, 2), (4, 4) or a first weight and a secondweight each having 1 or a multiple of 2.

For example, inter prediction may be performed with respect to theneighbor block of the top right of D and inter prediction may beperformed with respect to the neighbor block on the bottom left of D. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 3), (1, 7), (1, 15) or a first weight and a secondweight, a sum of which is a multiple of 2.

FIG. 16 shows an example in which the size of a block is 8×4 and N is 4which is the minimum value (height) of the width or height of the block.Referring to FIG. 16 , the final prediction block may be generated inorder of A and B.

When the final prediction block of A is generated, the final predictionblock may be generated thorough different weighted sum using Equation 2or Equation 3 depending on whether intra prediction is performed withrespect to the neighbor block on the top right or bottom left of A.Here, the top right or bottom left of A may be replaced with thelocations A to I of FIG. 11 .

For example, intra prediction may be performed with respect to theneighbor block on the top right of A and intra prediction may beperformed with respect to the neighbor block on the bottom left of A. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (3, 1), (7, 1), (15, 1), or the first weight and thesecond weight, a sum of which is a multiple of 2.

For example, intra prediction may be performed with respect to theneighbor block on the top right of A and inter prediction may beperformed with respect to the neighbor block on the bottom left of A. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 1), (2, 2), (4, 4) or a first weight and a secondweight each having 1 or a multiple of 2.

For example, inter prediction may be performed with respect to theneighbor block on the top right of A and intra prediction may beperformed with respect to the neighbor block on the bottom left of A. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 1), (2, 2), (4, 4) or a first weight and a secondweight each having 1 or a multiple of 2.

For example, inter prediction may be performed with respect to theneighbor block of the top right of A and inter prediction may beperformed with respect to the neighbor block on the bottom left of A. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 3), (1, 7), (1, 15) or a first weight and a secondweight, a sum of which is a multiple of 2.

When the final prediction block of B is generated, the final predictionblocks may be generated thorough different weighted sum using Equation 2or Equation 3 depending on whether intra prediction is performed withrespect to the neighbor block on the top right or bottom left (thebottom left of the neighbor block) of B. Here, the top right or bottomleft of B may be replaced with the locations A to I of FIG. 11 .

For example, intra prediction may be performed with respect to theneighbor block on the top right of B and intra prediction may beperformed with respect to the neighbor block on the bottom left of B. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be may be (3, 1), (7, 1), (15, 1), or the first weightand the second weight, a sum of which is a multiple of 2.

For example, intra prediction may be performed with respect to theneighbor block on the top right of B and inter prediction may beperformed with respect to the neighbor block on the bottom left of B. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 1), (2, 2), (4, 4) or a first weight and a secondweight each having 1 or a multiple of 2.

For example, inter prediction may be performed with respect to theneighbor block on the top right of B and intra prediction may beperformed with respect to the neighbor block on the bottom left of B. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 1), (2, 2), (4, 4) or a first weight and a secondweight each having 1 or a multiple of 2.

For example, inter prediction may be performed with respect to theneighbor block of the top right of B and inter prediction may beperformed with respect to the neighbor block on the bottom left of B. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 3), (1, 7), (1, 15) or a first weight and a secondweight, a sum of which is a multiple of 2.

FIG. 17 shows an example in which the size of a block is 4×8 and N is 4which is the minimum value (weight) of the width or height of the block.Referring to FIG. 17 , the final prediction block may be generated inorder of A and B.

When the final prediction block of A is generated, the final predictionblocks may be generated thorough different weighted sum using Equation 2or Equation 3 depending on whether intra prediction is performed withrespect to the neighbor block on the top right or bottom left of A.Here, the top right or bottom left of A may be replaced with thelocations A to I of FIG. 11 .

For example, intra prediction may be performed with respect to theneighbor block on the top right of A and intra prediction may beperformed with respect to the neighbor block on the bottom left of A. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (3, 1), (7, 1), (15, 1), or the first weight and thesecond weight, a sum of which is a multiple of 2.

For example, intra prediction may be performed with respect to theneighbor block on the top right of A and inter prediction may beperformed with respect to the neighbor block on the bottom left of A. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 1), (2, 2), (4, 4) or a first weight and a secondweight each having 1 or a multiple of 2.

For example, inter prediction may be performed with respect to theneighbor block on the top right of A and intra prediction may beperformed with respect to the neighbor block on the bottom left of A. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 1), (2, 2), (4, 4) or a first weight and a secondweight each having 1 or a multiple of 2.

For example, inter prediction may be performed with respect to theneighbor block of the top right of A and inter prediction may beperformed with respect to the neighbor block on the bottom left of A. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 3), (1, 7), (1, 15) or a first weight and a secondweight, a sum of which is a multiple of 2.

When the final prediction block of B is generated, the final predictionblock may be generated thorough different weighted sum using Equation 2or Equation 3 depending on whether intra prediction is performed withrespect to the neighbor block on the top right (the top right of theneighbor block) or bottom left of B. Here, the top right or bottom leftof B may be replaced with the locations A to I of FIG. 11 .

For example, intra prediction may be performed with respect to theneighbor block on the top right of B and intra prediction may beperformed with respect to the neighbor block on the bottom left of B. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be may be (3, 1), (7, 1), (15, 1), or the first weightand the second weight, a sum of which is a multiple of 2.

For example, intra prediction may be performed with respect to theneighbor block on the top right of B and inter prediction may beperformed with respect to the neighbor block on the bottom left of B. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 1), (2, 2), (4, 4) or a first weight and a secondweight each having 1 or a multiple of 2.

For example, inter prediction may be performed with respect to theneighbor block on the top right of B and intra prediction may beperformed with respect to the neighbor block on the bottom left of B. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 1), (2, 2), (4, 4) or a first weight and a secondweight each having 1 or a multiple of 2.

For example, inter prediction may be performed with respect to theneighbor block of the top right of B and inter prediction may beperformed with respect to the neighbor block on the bottom left of B. Atthis time, (the first weight, the second weight) used in Equation 2 orEquation 3 may be (1, 3), (1, 7), (1, 15) or a first weight and a secondweight, a sum of which is a multiple of 2.

FIG. 18 is a view illustrating an image decoding method according to anembodiment of the present invention.

Referring to FIG. 18 , the decoder may generate an inter predictionblock by performing inter prediction with respect to the current block(S1810).

In addition, the decoder may generate an intra prediction block byperforming intra prediction with respect to the current block (S1820).

Specifically, the decoder may generate the intra prediction block usinga predefined intra prediction mode.

Here, the predefined intra prediction mode may be a non-directionalintra prediction mode (e.g., a PLANAR intra prediction mode).

In addition, the decoder may determine a first weight and a secondweight (S1830). Specifically, the first weight and the second weight maybe determined based on the prediction mode of at least one neighborblock adjacent to the current block.

For example, the first weight and the second weight may be determinedbased on the number of neighbor blocks decoded in the intra predictionmode among the plurality of neighbor blocks adjacent to the currentblock. Here, the plurality of neighbor blocks may include a leftneighbor block adjacent to the left of the current block and a topneighbor block adjacent to the top of the current block.

In addition, the decoder may generate a final prediction block byrespectively applying the first weight and the second weight to theinter prediction block and the intra prediction block (S1840).Specifically, the decoder may generate the final prediction block usingEquation 2 or Equation 3 above.

Meanwhile, the decoder may perform step of determining whether theprediction mode of the current block is a combined inter intra modebefore performing the above-described steps.

When the prediction mode of the current block is the combined interintra mode, the decoder may not perform at least one of DMVR(Decoder-side Motion Vector Refinement), BDOF (Bi-Directional OpticalFlow), or BCW (Bi-prediction with CU-level weight).

In order to derive the same prediction result as the decoder in theencoder, the image encoding method equal to the image decoding method ofFIG. 18 may be performed.

The bitstream generated by the image encoding method of the presentinvention may be temporarily stored in a non-transitorycomputer-readable recording medium and may be a bitstream encoded by theabove-described image encoding method.

Specifically, a non-transitory computer-readable recording mediumstoring a bitstream generated by a method of encoding an image. Themethod of encoding the method may include generating an inter predictionblock by performing inter prediction with respect to a current block,generating an intra prediction block by performing intra prediction withrespect to the current block, determining a first weight and a secondweight, and generating a final prediction block by respectively applyingthe first weight and the second weight to the inter prediction block andthe intra prediction block. Here, the generating of the intra predictionblock includes generating the intra prediction block using a predefinedintra prediction mode.

The above embodiments may be performed in the same method in an encoderand a decoder.

At least one or a combination of the above embodiments may be used toencode/decode a video.

A sequence of applying to above embodiment may be different between anencoder and a decoder, or the sequence applying to above embodiment maybe the same in the encoder and the decoder.

The above embodiment may be performed on each luma signal and chromasignal, or the above embodiment may be identically performed on luma andchroma signals.

A block form to which the above embodiments of the present invention areapplied may have a square form or a non-square form.

The above embodiment of the present invention may be applied dependingon a size of at least one of a coding block, a prediction block, atransform block, a block, a current block, a coding unit, a predictionunit, a transform unit, a unit, and a current unit. Herein, the size maybe defined as a minimum size or maximum size or both so that the aboveembodiments are applied, or may be defined as a fixed size to which theabove embodiment is applied. In addition, in the above embodiments, afirst embodiment may be applied to a first size, and a second embodimentmay be applied to a second size. In other words, the above embodimentsmay be applied in combination depending on a size. In addition, theabove embodiments may be applied when a size is equal to or greater thata minimum size and equal to or smaller than a maximum size. In otherwords, the above embodiments may be applied when a block size isincluded within a certain range.

For example, the above embodiments may be applied when a size of currentblock is 8×8 or greater. For example, the above embodiments may beapplied when a size of current block is 4×4 only. For example, the aboveembodiments may be applied when a size of current block is 16×16 orsmaller. For example, the above embodiments may be applied when a sizeof current block is equal to or greater than 16×16 and equal to orsmaller than 64×64.

The above embodiments of the present invention may be applied dependingon a temporal layer. In order to identify a temporal layer to which theabove embodiments may be applied, a corresponding identifier may besignaled, and the above embodiments may be applied to a specifiedtemporal layer identified by the corresponding identifier. Herein, theidentifier may be defined as the lowest layer or the highest layer orboth to which the above embodiment may be applied, or may be defined toindicate a specific layer to which the embodiment is applied. Inaddition, a fixed temporal layer to which the embodiment is applied maybe defined.

For example, the above embodiments may be applied when a temporal layerof a current image is the lowest layer. For example, the aboveembodiments may be applied when a temporal layer identifier of a currentimage is 1. For example, the above embodiments may be applied when atemporal layer of a current image is the highest layer.

A slice type or a tile group type to which the above embodiments of thepresent invention are applied may be defined, and the above embodimentsmay be applied depending on the corresponding slice type or tile grouptype.

In the above-described embodiments, the methods are described based onthe flowcharts with a series of steps or units, but the presentinvention is not limited to the order of the steps, and rather, somesteps may be performed simultaneously or in different order with othersteps. In addition, it should be appreciated by one of ordinary skill inthe art that the steps in the flowcharts do not exclude each other andthat other steps may be added to the flowcharts or some of the steps maybe deleted from the flowcharts without influencing the scope of thepresent invention.

The embodiments include various aspects of examples. All possiblecombinations for various aspects may not be described, but those skilledin the art will be able to recognize different combinations.Accordingly, the present invention may include all replacements,modifications, and changes within the scope of the claims.

The embodiments of the present invention may be implemented in a form ofprogram instructions, which are executable by various computercomponents, and recorded in a computer-readable recording medium. Thecomputer-readable recording medium may include stand-alone or acombination of program instructions, data files, data structures, etc.The program instructions recorded in the computer-readable recordingmedium may be specially designed and constructed for the presentinvention, or well-known to a person of ordinary skilled in computersoftware technology field. Examples of the computer-readable recordingmedium include magnetic recording media such as hard disks, floppydisks, and magnetic tapes; optical data storage media such as CD-ROMs orDVD-ROMs; magneto-optimum media such as floptical disks; and hardwaredevices, such as read-only memory (ROM), random-access memory (RAM),flash memory, etc., which are particularly structured to store andimplement the program instruction. Examples of the program instructionsinclude not only a mechanical language code formatted by a compiler butalso a high level language code that may be implemented by a computerusing an interpreter. The hardware devices may be configured to beoperated by one or more software modules or vice versa to conduct theprocesses according to the present invention.

Although the present invention has been described in terms of specificitems such as detailed elements as well as the limited embodiments andthe drawings, they are only provided to help more general understandingof the invention, and the present invention is not limited to the aboveembodiments. It will be appreciated by those skilled in the art to whichthe present invention pertains that various modifications and changesmay be made from the above description.

Therefore, the spirit of the present invention shall not be limited tothe above-described embodiments, and the entire scope of the appendedclaims and their equivalents will fall within the scope and spirit ofthe invention.

INDUSTRIAL APPLICABILITY

The present invention may be used to encode or decode an image.

1. A method of decoding an image, the method comprising: generating aninter prediction block by performing inter prediction with respect to acurrent block; generating an intra prediction block by performing intraprediction with respect to the current block; determining a first weightand a second weight; generating a final prediction block by respectivelyapplying the first weight and the second weight to the inter predictionblock and the intra prediction block; reconstructing a residual blockfrom a bitstream; and generating a reconstruction block of the currentblock based on the final prediction block and the residual block,wherein the generating of the intra prediction block includes generatingthe intra prediction block using a predefined intra prediction mode,wherein the determining of the first weight and the second weightincludes determining the first weight and the second weight based on thenumber of neighbor blocks decoded in an intra prediction mode among aplurality of neighbor blocks adjacent to the current block, and whereinthe plurality of neighbor blocks includes a left neighbor block adjacentto a left of the current block and a top neighbor block adjacent to atop of the current block.
 2. A method of encoding an image, the methodcomprising: generating an inter prediction block by performing interprediction with respect to a current block; generating an intraprediction block by performing intra prediction with respect to thecurrent block; determining a first weight and a second weight;generating a final prediction block by respectively applying the firstweight and the second weight to the inter prediction block and the intraprediction block; and generating a residual block based on the finalprediction block and encoding the residual block, wherein the generatingof the intra prediction block includes generating the intra predictionblock using a predefined intra prediction mode, wherein the determiningof the first weight and the second weight includes determining the firstweight and the second weight based on the number of neighbor blocksdecoded in an intra prediction mode among a plurality of neighbor blocksadjacent to the current block, and wherein the plurality of neighborblocks includes a left neighbor block adjacent to a left of the currentblock and a top neighbor block adjacent to a top of the current block.3. A non-transitory computer-readable recording medium for storing abitstream generated by an image encoding method, the image encodingmethod comprising: generating an inter prediction block by performinginter prediction with respect to a current block; generating an intraprediction block by performing intra prediction with respect to thecurrent block; determining a first weight and a second weight; andgenerating a final prediction block by respectively applying the firstweight and the second weight to the inter prediction block and the intraprediction block; and generating a residual block based on the finalprediction block and encoding the residual block, wherein the generatingof the intra prediction block includes generating the intra predictionblock using a predefined intra prediction mode, wherein the determiningof the first weight and the second weight includes determining the firstweight and the second weight based on the number of neighbor blocksdecoded in an intra prediction mode among a plurality of neighbor blocksadjacent to the current block, and wherein the plurality of neighborblocks includes a left neighbor block adjacent to a left of the currentblock and a top neighbor block adjacent to a top of the current block.